tag:blogger.com,1999:blog-55579139779131483662024-03-13T23:15:44.335-07:00196,800 Revolutions Per MinuteCombating misconceptions about firearms, and some other neat stuff too.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.comBlogger40125tag:blogger.com,1999:blog-5557913977913148366.post-19909572766341686322016-01-02T04:01:00.003-08:002016-01-07T16:00:52.877-08:00Frontal Area (Almost) Doesn't Matter For Stopping PowerThis is a segment of <a href="http://www.thefirearmblog.com/blog/2016/01/01/spec-ops-doctor-rather-shot-with-ak-47-over-m16/#comment-2435770841">a comment I made on TFB,</a> preserved here because the argument comes up so damned often:<br />
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Those type of surface area calculations have virtually no value by themselves in a discussion of terminal effectiveness, so far as I can tell. I suspect they were popularized by Dr. Gary Roberts, who should stick to dentistry, I reckon. The fact is that these calibers do not generally speaking carve neat holes. Take a simple piece of evidence of this the "wound" created in a piece of paper by FMJRN .38" caliber pistol rounds, versus those of WC .38" caliber pistol rounds. Despite having the exact same frontal area, the displacement of paper is very different. If you do not know what I am talking about, there is a photo below illustrating it:<br />
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<a href="http://exclusive.multibriefs.com/images/exclusive/0903bullet2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://exclusive.multibriefs.com/images/exclusive/0903bullet2.jpg" /></a></div>
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It's obvious that paper is not human tissue, of course, but the point is made. Bullets - wadcutters aside - don't cut neat chunks of flesh out of a target. They stretch and bend the tissue around them, including paper, which is fairly brittle in comparison to human fat, muscle, and other tissues. If this stretching is occurring, we would not expect to see very much difference at all between a .30" caliber "through and through" FMJ wound and a .22" caliber one, and indeed, we don't. In fact, doctors have a difficult time telling them apart, until the bullet is extracted. Indeed, look at the target again. The .38 and .45 wadcutter holes are easily differentiated, but the .38 and .45 FMJ holes much less so.<br />
One should consider carefully the example above: The wadcutters carve the paper like a hole punch, while the FMJs stretch and bend the paper, making a much smaller, ragged hole. Given this, is it any wonder that the .38 Special semi-wadcutter bullet has a better reputation for terminal effect than other, comparable projectiles?Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com13tag:blogger.com,1999:blog-5557913977913148366.post-71822384665779158542015-07-20T15:49:00.000-07:002015-07-23T15:13:30.723-07:00Some Further Arguments About The GPC/6.Xmm Infantry Rifle AmmunitionI've done a little arguing here and there on forums about the general purpose cartridge (GPC) idea, and the closely related but not necessarily identical 6.Xmm rifle cartridge concept, and I feel it is worth reposting some of the posts I've made for reference here on the blog.<br />
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First, here's a discussion of how shorter barrels negatively impact the GPC concept, relative to 7.62 NATO. One might think that if a GPC equals 7.62 NATO in capability from a 24" barrel, that the same round should equal 7.62 NATO if both are shot from 16.5" barrels, right? <a href="http://196800revolutionsperminute.blogspot.com/2014/03/general-purpose-cartridge-revisited.html">This is not in fact the case.</a> What can be seen here is that 7.62 NATO retains its energy at range more gracefully as barrel lengths get shorter than a 6.5mm round.<br />
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The way the model is set up, 7.62 NATO data was pulled directly from empirical figures, and in either case - 24 or 16.5" barrel - the 6.5mm's velocity was adjusted to match the energy at a kilometer.<br />
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Perhaps this is somewhat of an opaque example, and I should later go into greater depth exploring it, but for now, I am just reposting it here:<br />
<blockquote class="tr_bq" style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">
Alright, here you go guys, here's a demonstration of how shorter barrels hurts the GPC more than 7.62 NATO. Let's use <a href="http://rifleshooter.com/2014/12/308-winchester-7-62x51mm-nato-barrel-length-versus-velocity-28-to-16-5/" style="color: #990000;" target="_blank">Rifleshooter's test of Winchester contract overrun</a> as a baseline. So, from a 24" barrel, that ammunition produces a muzzle velocity of 2909 ft/s. Here's what it looks like at a klick:<br />
<img alt="" src="http://i.imgur.com/8GaeG4E.png" /><br />
445.9 J, that's what we have to match with the GPC. I am using a 6.5mm near-Balle D homologue for this, i7 FF of .889 and a G7 BC of .249, 108gr/7g. I adjusted the velocity until it matched 7.62 at a klick from a 24" barrel:<br />
<img alt="" src="http://i.imgur.com/ZuBQNou.png" /><br />
That the MV ended up identical to .264 USA is coincidence. Note that the projectile used is much, much finer. So the round has to produce 2,875 ft/s from a 24" barrel to match 7.62 using that exceptionally fine bullet. Now, from a 16.5" barrel, the Winchester produces 2,682 ft/s:<br />
<img alt="" src="http://i.imgur.com/rY5wBGA.png" /><br />
410.3 J. So we have to match that with our 6.5mm:<br />
<img alt="" src="http://i.imgur.com/qWMGyS6.png" /><br />
So there you have it. Internal ballistics aside, even the best 6.5mm GPC loses out to 7.62 NATO as barrels get shorter. Note that 7.62 NATO retained 92% of its muzzle velocity when the barrel was shortened by 7.5", but to catch up to that, the GPC has to cling to over 97% of its muzzle velocity.</blockquote>
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Next is a post I wrote addressing the idea that 7.62x54R "overmatches" 7.62 NATO to any substantial degree. This is a commonly held view, but <a href="http://forums.delphiforums.com/autogun/messages/?msg=6282.13">it appears to be the product of some suspect ballistic coefficient figures posted to 7.62x54r.net:</a><br />
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<blockquote class="tr_bq" style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">
The most common light steel cored ball ammo has a BC very similar to M80, and generally speaking a slightly lower or equal muzzle velocity.<br />
I would be very surprised to hear that the more exotic types - especially the 7N1 - were at all common in Afghanistan, and I also have doubts about their "legendarily" high BCs.<br />
For example, let's take the 7N1 "sniper" ball, pulled bullet alongside propellant and case below:<br />
<img alt="" src="http://7.62x54r.net/MosinID/A0303.jpg" /><br />
Clearly not a bad bullet shape, but how good is it? The ".249 G7 BC" figure was translated from G1 BC from 7.62x54r.net's website, the same site where I took this image. In fact, the round in this image was pulled from the very same sample of rounds tested. So there is no question that the data matches the projectile. But does the data make sense? In short, no. A .249 G7 BC means this 152gr projectile has a .907 i7 FF. What other projectiles have about a .907 i7 FF? Well:<br />
<img alt="" src="http://upload.wikimedia.org/wikipedia/commons/1/17/German_7.92mm_Ss_198gr_FMJBT.jpg" /><br />
The best, most streamlined examples of the 7.9mm sS Patrone had an i7 FF of about .906. And,<br />
<img alt="" src="http://www.thefirearmblog.com/blog/wp-content/uploads/2015/06/Berger-264-Caliber-130-Grain-AR-Hybrid-OTM-Tactical-660x319.jpg" /><br />
The new Berger 130 AR Hybrid ogive bullet, with its i7 FF of .919.<br />
Both of these bullets are considerably better streamlined than the 7N1. Coming at it the other way, let's look at the plain-jane steel-cored light ball projectile, which according to 7.62x54r.net has a BC (converted) of .163 G7, which would give it a hilariously poor i7 FF of 1.34:<br />
<img alt="" src="http://7.62x54r.net/MosinID/A0013.jpg" /><br />
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Note that the ogive is identical to the tangent ogive of the 7N1, and that the boattail is not too much less severe.<br />
Because of this, I cannot consider 7.62x54r.net's BC figure for the 7N1 to be likely. It's much, much more likely that the i7 FF of these projectiles is in the 1.10-.98 range, giving the 7N1 a BC of .229 G7, at best. Given the lower velocity, this makes it ballistically extremely similar to 7.62x51.<br />
If you look at Hodgdon's numbers for 7.62x54R and mate those with 7.62x54r.net's BC figure for the 7N1, the round looks quite scary, but the velocities produced by actual military ammunition, coupled with more realistic estimates of the BCs of military projectiles give much more sedate ballistics.</blockquote>
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The only way that the Russian caliber could be overmatching 7.62 NATO substantially would be if Russian AP ammunition were finding its way into the hands of enemy combatants. Not only is there little evidence that this is happening, it means the correct response would be to field a round with more penetration than current M80 Ball - which is exactly what the US Army has done with the M80A1.<br />
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<a href="http://forums.delphiforums.com/autogun/messages/?msg=6282.22">Another post</a> addresses the danger of over-emphasizing the need for fine projectile shapes. Certainly, projectiles should have as fine a shape as feasible, however often a fine shape is not compatible with other requirements, such as the shape of an armor penetrating core:<br />
<blockquote class="tr_bq" style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">
That doesn't really make sense. The shorter ogive was chosen because the ogive they were using - retained from the earlier .30-06 M2 - was short enough that the bullet could be buried more deeply in the case. Later, the form factor was improved by going to a 10-caliber secant ogive.<br />
The 7.62x51 NATO was further specifically designed for a 700m danger space requirement, falsifying what you said about it being designed for shorter ranges. Even if I've misunderstood you and you were referring to 5.56mm, <em>that</em> round was designed for a 500m requirement.<br />
You cite the 7.9x57 sS Patrone, but that round is the exception, rather than the rule. The 7.9x57 was not designed with an ogive that long; the earlier S Patrone being almost identical in shape to the aforementioned M2 Ball. The fine ogive of the sS ball was applied later, and they mostly got away with it because the 8mm projectile was so wide. The AP core for the SmK round is in fact smaller in diameter than that of the .30 caliber M2 AP, despite the projectile being .381mm wider. It could not be any wider, or else it wouldn't fit into the fine form factor - the same form factor as the sS Patrone.<br />
So you can see that having a fine ogive has consequences, which is why even in rounds like the 6.5x55 Swedish Skp. Ptr. 41 the ogive is not that long, surprisingly. This all goes back to what I've been saying for some time now; while it's nice to have a fine ogive shape, at the end of the day having the finest projectile shape with the lowest i7 FF puts limitations on your projectile design, and less elegant projectiles not bound by those limitations may actually perform better.<br />
<img alt="" src="http://world.guns.ru/userfiles/images/ammo/ammo_pics/1288325667.jpg" /></blockquote>
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It's also worth noting that the shape of the projectile of one kind of round influences the shape of others. A poorly shaped tracer projectile may not match the trajectory of the ball round closely enough, and an AP round that required a different zero than the ball ammunition would be much less useful than one that didn't. At the end of the day, all these requirements must be met, and these can drive poorer projectile shapes than the GPC crowd often assumes.<br />
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<a href="http://forums.delphiforums.com/autogun/messages/?msg=6314.107">This next post</a> is an explanation of why it is difficult or impossible to compensate for a lack of MG teams by augmenting the capabilities of the rifleman's weapon:<br />
<blockquote class="tr_bq">
<span style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">I think it's worthwhile, too, to take a tangent and discuss why rifles firing more powerful ammunition cannot compensate for a lack of machine gun teams. I'll make it short, I hope.</span><br style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;" /><span style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">The machine gun team consists of the gunner and assistant gunner, which - like a sniper and his spotter - gives it much better situational awareness than a single rifleman. Both </span><a href="http://www.globalsecurity.org/military/library/policy/army/fm/3-22-68/c04.htm" style="background-color: white; color: #990000; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;" target="_blank">the gunner and assistant gunner are well-trained</a><span style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;"> to make the most of this relationship, and are equipped to provide fire at longer ranges, and are given a tripod and tracer rounds to assist them in this. When you hear things like "800m is crew served weapons range" this is what is meant. Two men with the right equipment can provide accurate fire out to much longer distances than is possible with one person with a rifle, in combat conditions.</span><br style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;" /><span style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">For example, let's examine what happens when the trigger is pulled against a target at longer ranges (over 200 yards). The hammer falls, and the cartridge ignites. Immediately, the gun begins to recoil under great acceleration, and flash and blast emanates from the weapon's muzzle, obscuring vision for just a moment. Within that moment the round has traveled a considerable distance downrange, and the further out it impacts, the less visible the impact is, both because the impact is more distant and because there is less velocity to the impact. The round will most likely not hit the target, due to a wide variety of errors that are impossible to consistently compensate for on the first round. If this is a rifleman, he is likely to blink during firing, and the recoil of the gun disturbs his sight picture - his rifle is after all not equipped with a tripod, and his ammunition is not (usually) traced, so he has a harder time distinguishing the trajectory of his fire. Now, if this is a machine gun team, the AG is sitting there watching all this happen. He has seen where the round has gone, as much as is possible, and the gun is properly equipped with a tripod and tracers, not to mention a T&E mechanism. Being a machine gun, too, fire comes in bursts, improving the probability of a hit. The AG is dedicated to assisting the gunner in putting out accurate fire - he has no other job (besides keeping the gun fed). His eyes help the gunner pick out targets, and he's able to tell the gunner immediate feedback that the gunner otherwise would not have - like when a civilian is sighting a rifle in on the range, having a spotter is a huge help; at longer ranges it's essential.</span><br style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;" /><span style="background-color: white; font-family: Verdana, Arial, Helvetica, Geneva, Swiss, Arial, Helvetica, Geneva, sans-serif; font-size: 12px;">So for this reason, I strongly contest the idea that a lack of MG teams can be compensated for by issuing more powerful rifles. No, a lack of MG teams can only be compensated for by fielding more MG teams.</span></blockquote>
The subjects of these posts will probably be combined at some point in a larger more in-depth article for The Firearm Blog, but with the Light Rifle and daily posts currently occupying my time, I cannot say when that post will arrive.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com14tag:blogger.com,1999:blog-5557913977913148366.post-57345290555080904262015-05-08T19:21:00.003-07:002015-05-08T19:45:36.990-07:00An Evaluation of The Faxon Firearms ARAK-21 RifleAt the event Faxon Firearms hosted on January 22nd of this year, I had the chance to shoot some examples of the Faxon ARAK-21 rifles, especially two rifles, which I will call Fifty-Two in 5.56mm and Oh Five in .308 Winchester (the latter of which I am given to understand is a prototype). I shot other ARAK-21s, but what I will say here concerns these two in particular.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgct58N6kI63OBdQLCCrnPIrWu3vM_K8ltlYR1UAaV_7XaTPEXPiyIrm_sycdgQ0NyCQzd-V2e_2Kti3udxe-X_MWh32Kfu2TA-f1eUG5oRpD2-DPF6KXDHVV3qA6SL-7Ny08K4S2i0SXo4/s1600/0122152029b.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgct58N6kI63OBdQLCCrnPIrWu3vM_K8ltlYR1UAaV_7XaTPEXPiyIrm_sycdgQ0NyCQzd-V2e_2Kti3udxe-X_MWh32Kfu2TA-f1eUG5oRpD2-DPF6KXDHVV3qA6SL-7Ny08K4S2i0SXo4/s640/0122152029b.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fifty-Two, with EoTech, suppressor, ACE folding stock, and short handguard.</td></tr>
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With Fifty-Two, I had numerous malfunctions, mostly of a minor kind that was nonetheless indicative of more serious problems the rifle may have. The weapon had a tan finish, was suppressed, with a short handguard, ACE folding stock, and it mounted an EoTech holographic sight. I assume the barrel was in the 13-16" range; I do not know exactly how long. I chose to shoot this weapon because it was in 5.56mm, had a short handguard (so I could make a more fair weight comparison to other rifles), and because I wanted to get as much trigger time on one rifle as possible. I was not led to shoot this particular rifle by any Faxon employee or anyone else. I estimate I put less than a hundred rounds through Fifty-Two. It was the rifle I shot the most at the event.<br />
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Fifty-Two had already been shot before I reached it; I am not sure when it was last cleaned, but thanks to the suppressor the rifle already had a fine film of powder residue inside the receiver. I did not consider this residue further in my analysis.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDkeqwkOGtSkmBWpCdhEOS4MArYbAU1ZueTMl1AtT5UOF8FvBW2SJ8uiv0z1LMZgCFGJjTPsHprb2zYrk0D9j-xX6Mtsm0mT6zPOpELcFdZ3NoJ3c5dRlazD-rAXACDIGWquDsp0P_vnA1/s1600/0122152031c.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhDkeqwkOGtSkmBWpCdhEOS4MArYbAU1ZueTMl1AtT5UOF8FvBW2SJ8uiv0z1LMZgCFGJjTPsHprb2zYrk0D9j-xX6Mtsm0mT6zPOpELcFdZ3NoJ3c5dRlazD-rAXACDIGWquDsp0P_vnA1/s640/0122152031c.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fifty-Two's receiver was very dirty, but no dirtier than I would expect from a suppressed AR-15 after firing a few hundred rounds.</td></tr>
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I first made some ergonomic observations about the rifle, before shooting it. Even with the ACE folder, which I hoped would add some weight to the rifle and improve its balance, it was very front heavy; I found this created significant discomfort when handling the weapon, especially when compared to an M4-style carbine. Other rifles of the current generation are also front-heavy, but I would consider Fifty-Two to be exceptional in this regard.<br />
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I noted the rifle's charging handle sits forward and very low over the rail, and folds. I found the charging handle difficult to grab in this position; essentially I could only hold onto the very tip. Before I began shooting, I noted the bolt had to be given a running start to go into battery. When charging the rifle, this became a serious problem. If Fifty-Two has a bolt-closure device, I did not discover it (I was later informed that the ARAK-21 does not have a bolt-closure device). For comparison, even AR-15s without forward assist devices can be assisted into battery by pushing against the carrier with the thumb; there is no ability to do this with Fifty-Two. While I would normally consider pushing the bolt into battery a minor problem, I found that Fifty-Two presented serious problems when trying to correct this malfunction. The bolt head was able to capture cartridges and strip them from the magazine through friction alone, causing combined bolt-over-base/double-feed malfunctions when trying to close the bolt. I had to either remove the magazine and try to feed a new round, or carefully short-stroke the gun to achieve battery; this happened several times.<br />
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Fifty-Two, and all other rifles I have fired, had serious heating issues. Even firing magazines of only 5 rounds each, which was how ammunition was provided at the event, the rifles retained heat and quickly became uncomfortable to hold with bare hands. This happened much sooner than I would have expected in a similar string of fire with my Colt 6920 (which uses old-style Magpul MOE handguards). The pace of fire was very tame. I would go to the line, shoot one or two magazines with five rounds a piece, return to the ammunition station, pick up one or two more magazines of five rounds, and repeat. I did not try to do this as fast as I could. Despite this, the rifle heated up substantially. It also held the heat long after I set it down to cool.<br />
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The recoil of Fifty Two, and all other 5.56mm ARAK-21s I shot on the 22nd, was not so mild as reviews of this firearm led me to believe. I did not shoot an AR-15 at the event, but it's my opinion that the ARAK-21 recoils somewhat harder than my 6920. The ARAK-21 most likely has softer recoil than standard AKM-type rifles, in my opinion. Given the weight of the rifle, I would consider its recoil characteristics acceptable but marginal.<br />
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The malfunctions I experienced with Fifty-Two were mostly failures to engage the bolt hold open device. The rifle would tend to overshoot the bolt catch and be stopped by the follower of the magazine. These malfunctions are indicative of a very high cyclic rate and high friction during feeding, which is consistent with the observations I made on how fast the bolt seemed to be cycling. I did not bring my high speed camera, and thus could not confirm the cyclic rate.<br />
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I field-stripped Fifty Two without the aid of a Faxon representative. However, I did feel there were improvements that could be made to the field-stripping process. Depending on how it is counted, field stripping requires four or five steps to complete, while assembly requires five steps. During assembly, I found the enclosed receiver hindered alignment of the piston with the gas tube, and that it was possible to get the bolt carrier inside the receiver without having the piston properly aligned in the tube. The delicacy needed to get the piston and bolt carrier aligned in their respective homes caused me more than once to compress the bolt during assembly inadvertently. Unlike an AR-15, it is possible to insert the bolt assembly into the receiver with the bolt in the rearward locked position, which prevents correct assembly. After I had disassembled the gun the first time, I still found the process of field strip and reassembly to be a balancing act. It is my opinion that both the AK and AR-15 are much easier to strip and reassemble than Fifty-Two, especially under duress. Fifty-Two was the only ARAK-21 I field stripped.<br />
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Fifty-Two had a gas regulator. After firing a modest number of rounds, I found the gas system too hot and too small to manipulate. Given the rifle's high cyclic rate, I feel this is a significant drawback. The rifle when I got it had the cyclic rate turned all the way to the right, if one is looking down the sights. I do not know whether that position is all the way on or at the minimum setting.<br />
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I also fired rifle Oh Five in .308 Winchester. This rifle suffered similar failures to go into battery as Fifty-Two. I shot far fewer rounds through Oh Five, perhaps ten or fifteen. My shooting with Oh Five was ended when the Fiocchi ammunition that was provided blew a primer out of the back of the case, sticking in the chamber and causing a double feed. Examination of brass fired through Oh Five showed signs of pressure: The imprint of the dual ejectors was visible on the case head, having been etched through the headstamp. This is not the first time I have seen signs of dangerous pressure from Fiocchi ammunition. It is my opinion that these malfunctions were not the result of any flaw in the rifle, but rather the ammunition manufacturer's fault. At this point, I called a representative over and he retired the rifle for the day.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoC33cu_VnxyBtFIX-KENppAUkqeVi_h14ee2MyBUrCeUjLYeyG2_IKJcXQBEZ05BBoi6Qm4WJj0wD2jj-gMirnUNzsueMeHw7Wp_ERNLAlEgOnL4elHSWwfNWgxqKsKu0hZpgliPZSCS4/s1600/0122152050a.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoC33cu_VnxyBtFIX-KENppAUkqeVi_h14ee2MyBUrCeUjLYeyG2_IKJcXQBEZ05BBoi6Qm4WJj0wD2jj-gMirnUNzsueMeHw7Wp_ERNLAlEgOnL4elHSWwfNWgxqKsKu0hZpgliPZSCS4/s640/0122152050a.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Oh Five, with a blown-out primer. I have no reason to believe this was the fault of the rifle.</td></tr>
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I have provided pictures of a little less than half of the malfunctions I encountered in shooting less than 100 rounds, embedded below. Each picture documents a separate malfunction. I have also included some pictures of Fifty-Two's condition during firing, showing how it was configured and the dirt inside of the receiver.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQmDSEZSR2ZqegmIZV2vhEsj4jcOJG9ozwzMH_PAbc-87_43H7IMUDQwjcY1yQzUoB8qyivDGLhl75y9ahCplpqpfsfxq5KoMSqKzeQg-XvTIXGMSvPqijY7Ahc8lKtLBI3seBnsf12Y0_/s1600/0122152022.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQmDSEZSR2ZqegmIZV2vhEsj4jcOJG9ozwzMH_PAbc-87_43H7IMUDQwjcY1yQzUoB8qyivDGLhl75y9ahCplpqpfsfxq5KoMSqKzeQg-XvTIXGMSvPqijY7Ahc8lKtLBI3seBnsf12Y0_/s640/0122152022.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A typical malfunction in Fifty-Two was for the bolt to skip over the cartridge base and try to feed it into the chamber through friction from the bolt lugs. Skipping over the cartridge base is a sign of either worn out magazines, which is unlikely, or a rifle that is running far too fast.</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR9inQpVhzE-vkRhY_sR7x_NerdW6V2QvNszxOslNQBrNs1R6AjQ6qLmzxJY1WQIMur1rJmVxDcczSZhFzaC-jZDEG_a4EMucBDVg7N6CQdzCrGdb6bXfLulflddWcxtiK0lHIvnLnfp6h/s1600/0122152026.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhR9inQpVhzE-vkRhY_sR7x_NerdW6V2QvNszxOslNQBrNs1R6AjQ6qLmzxJY1WQIMur1rJmVxDcczSZhFzaC-jZDEG_a4EMucBDVg7N6CQdzCrGdb6bXfLulflddWcxtiK0lHIvnLnfp6h/s640/0122152026.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The follower of the PMags provided produced enough friction against the bolt to stop the moving parts group. I believe this rifle cycled all the way to the rear, but skipped over the bolt hold open, another sign of a rifle that is running at too high a cyclic rate.</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqbrrSTOb-k_nufHIvumCyAkQT2xi0T83N3X1KJPdE6cDx6eklVb1yBmOu93JPuBuDCFojM-MLWdk2sWAS_qKwkNObldQkkWKpYmBD3U6jbNN2N6yVXRhQ51uO2seP7KqywQgJkMwi5s1D/s1600/0122152027a.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqbrrSTOb-k_nufHIvumCyAkQT2xi0T83N3X1KJPdE6cDx6eklVb1yBmOu93JPuBuDCFojM-MLWdk2sWAS_qKwkNObldQkkWKpYmBD3U6jbNN2N6yVXRhQ51uO2seP7KqywQgJkMwi5s1D/s640/0122152027a.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fifty-Two had considerable difficulty in locking and achieving battery. The bolt as seen here has stopped against the barrel, and failed to rotate. This malfunction is caused by a poor mass ratio, ejectors with too powerful springs, and friction in the receiver. In Fifty-Two, this malfunction was needlessly difficult to overcome, due to a lack of options for manually closing the bolt. Even AR-15s without forward assists can be manually assisted into battery by pushing with the thumb against the bolt carrier. Fifty-Two has a slick-sided bolt carrier that prevents such a maneuver.</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSeKrkOFgRjL9Irw8dVOBdZrrGIBqZJSRnCddHZ6fgShxIX4E7WU09MOT3gKwse35eICVL-LOYAAwW6tXTMBq_TzUT8P7oCWspe8FJq7H4JDWXXuFWeMLjPMnyveX8Twu64xfPcnZqIXoq/s1600/0122152027b.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSeKrkOFgRjL9Irw8dVOBdZrrGIBqZJSRnCddHZ6fgShxIX4E7WU09MOT3gKwse35eICVL-LOYAAwW6tXTMBq_TzUT8P7oCWspe8FJq7H4JDWXXuFWeMLjPMnyveX8Twu64xfPcnZqIXoq/s640/0122152027b.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">If I attempted to fix the bolt closure problem, this malfunction would often result. The first cartridge has remained in the chamber, never captured by the bolt's extractor, while the bolt has picked up the second cartridge through friction alone, causing a combination of bolt-over-base and double-feed malfunctions.<br />
<br />
<br />
<div style="text-align: left;">
<span style="font-size: small;">In my opinion, rifle Fifty-Two had some serious limitations. I am not sure exactly what segment of the market Faxon is targeting with the ARAK-21, but based on my shooting experiences on the 22nd of January with rifle Fifty-Two, I would not be able to recommend the ARAK-21 at this time. The rifle has serious issues stemming from a moving parts group that is too light and a mass ratio that is too poor. Faxon has tried to fix this by increasing the cyclic rate, but this most likely caused failures to eject and round skipping. It's probable that the Faxon engineers added the stronger ejectors and a gas regulator to solve those problems, but these in turn cause problems of their own. The Faxon ARAK-21 needs a total redesign to properly solve these issues.</span></div>
</td></tr>
</tbody></table>
Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com11tag:blogger.com,1999:blog-5557913977913148366.post-38034408513298400352015-04-09T14:02:00.004-07:002015-04-09T14:02:51.401-07:00The Taylor Knock-Out Index Is Useless<h3 style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; margin: 0px; position: relative;">
<b>This article was originally posted on another blog of mine in early 2012, but its content is more appropriate here, I think.</b></h3>
<span class="Apple-style-span" style="font-family: inherit;"><br /></span>
<span class="Apple-style-span" style="font-family: inherit;"><br /></span>
<span class="Apple-style-span" style="font-family: inherit;">The <a href="http://en.wikipedia.org/wiki/Taylor_KO_Factor">Taylor Knock-Out Index</a></span><span class="Apple-style-span" style="font-family: inherit;"> may be the single worst metric available for determining the effectiveness of small arms ammunition. Despite this, it sees relatively widespread use, usually to compare two calibers that are obviously in different potency classes.</span><br />
<br />
Why does the TKOI suck so bad?<br />
<br />
Well, let's do an experiment: What is the Taylor Knock Out Factor of the <a href="http://en.wikipedia.org/wiki/Lambert_Glacier">Lambert Glacier</a>?<br />
<br />
Of course, if you stand in front of the glacier, you'll hardly get vaporized. Glaciers, unless you're on poorly navigated, fast-moving ships, are largely harmless.<br />
<br />
And yet...<br />
<br />
The TKOF equation goes something like this:<br />
<br />
TKOF = (Mass x Velocity x Caliber)/7000<br />
<br />
Units in the normal Imperial grains, feet/sec, and inches, of course.<br />
<br />
So what's the TKO of the Lambert Glacier?<br />
<br />
Well, the Lambert Glacier is about 100km wide, 400km long, and 2.5km deep.<br />
<br />
To get volume, simply multiply:<br />
<br />
100,000 x 400,000 x 2,500<br />
<br />
= 100,000,000,000,000, or 100 trillion cubic meters volume.<br />
<br />
The density of ice is 916,700 g/m^3<br />
<br />
The mass of the Lambert Glacier is estimated to be approximately:<br />
<br />
91,670,000,000,000,000,000, or 91.67 sextillion grams mass.<br />
<br />
To find mass in grains, we simply multiply that by 15.43:<br />
<br />
91.67 x 15.43 x 1 sextillion<br />
<br />
=1,414,468,100,000,000,000,000, or 1.41 septillion grains mass.<br />
<br />
What is the caliber of the Lambert Glacier? We'll go ahead and take its width and height, and average them:<br />
<br />
(100,000m + 2,500m)/2<br />
<br />
= 51,250m<br />
<br />
Multiply by 3.28 and 12 to convert to inches:<br />
<br />
=2,017,200, or 2.02 million inches.<br />
<br />
What is the velocity of the Lambert Glacier?<br />
<br />
It varies, but one source quotes 400 to 800m/year Let's do some quick math:<br />
<br />
(400 + 800)/2<br />
<br />
= 600 m/yr<br />
<br />
600 m/yr x (1/(60x60x24x365)) yr/s<br />
<br />
= .000019 m/s<br />
<br />
.000019 m/s x 3.28 ft/m<br />
<br />
= .0000624, or 62.4 microfeet per second<br />
<br />
Now we can plug it all in!<br />
<br />
TKOF = (Mass x Velocity x Caliber)/7000<br />
<br />
TKOF = (1,414,468,100,000,000,000,000 x .0000624 x 2,017,200)/7000<br />
<br />
Before we solve this equation, we need some reference. For comparison, a 7.62x51mm rifle round has a TKOF of 17.787, and a .45 ACP pistol round has a TKOF of 12.568.<br />
<br />
Now, the Taylor Knock Out Factor of the Lambert Glacier is...<br />
<br />
Wait for it...<br />
<br />
Wait for it...<br />
<br />
<br />
<br />
25,434,829,886,052,571,429 TKOF! That's over twenty five sextillion on the TKOI! The Lambert Glacier should have destroyed the Earth by now!<br />
<br />
Quake in fear at the might of the Lambert Glacier, Destroyer of Worlds!<br />
<br />Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com3tag:blogger.com,1999:blog-5557913977913148366.post-46746487932006728862015-02-21T00:10:00.001-08:002015-02-21T00:10:17.305-08:00All My TFB Posts On The M1 GarandThe M1 Garand has been the subject of much of my writing over at TFB, since it is a fascinating design, at once revolutionary and deeply flawed. Its descendant, the M14, is to this day a controversial weapon; at once the longest serving rifle and the shortest serving <i>standard issue</i> rifle in U.S. military history, it's a rifle that will virtually always deeply polarize a conversation with its mention.<br /><br />I have decided to collect the posts I have so far done on the M1 Garand and the M14 rifle, for the convenience of my readership. They are, in chronological posting order, as follows:<br /><br /><a href="http://www.thefirearmblog.com/blog/2014/12/14/hindsight-is-3006-critique-of-the-m1-garand/">Hindsight Is 30/06: A Critique Of The M1 Garand</a><br />
<a href="http://www.thefirearmblog.com/blog/2014/12/16/making-m1-garand/">Making The M1 Garand</a><br />
<a href="http://www.thefirearmblog.com/blog/2014/12/23/great-rifle-controversy-1955/">The Great Rifle Controversy: 1955</a><br />
<a href="http://www.thefirearmblog.com/blog/2015/01/16/eight-reasons-selfloading-rifles-had-to-wait-for-john-garand/">Eight Reasons Selfloading Rifles Had To Wait For John Garand</a><br />
<a href="http://www.thefirearmblog.com/blog/2015/01/28/rifle-competition-us-vs-uk-1950-dtic/">Rifle Competition: US vs. UK in 1950 (DTIC)</a><br />
<a href="http://www.thefirearmblog.com/blog/2015/02/05/inrange-tvs-heinous-m1a-abuse/">InRange TV’s Heinous M1A Abuse</a><br />
<a href="http://www.thefirearmblog.com/blog/2015/02/10/small-caliber-book-reviews-u-s-rifle-m14-john-garand-m21/">Small Caliber Book Reviews: <i>U.S. Rifle M14, From John Garand To The M21</i></a><br />
<a href="http://www.thefirearmblog.com/blog/2015/02/14/two-usmc-marksmanship-training-films-compared/">Two USMC Marksmanship Training Films Compared</a><br />
<a href="http://www.thefirearmblog.com/blog/2015/02/20/the-m1-garand-dust-mud-1950/">The M1 Garand In The Dust And Mud, 1950</a><br />
<br />
I will definitely be posting more about these rifles in the future; in particular, I have upcoming a post on the "light rifle" concept, as full-power automatic infantry rifles were once called, which I hope will prove to be a definitive design case study on that concept.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0tag:blogger.com,1999:blog-5557913977913148366.post-31584521681736192452014-12-26T21:17:00.001-08:002015-02-21T00:11:26.340-08:00RPM Goes MainstreamIt's certainly true that I haven't posted an article here on 196,800 Revolutions Per Minute since May. Despite this, I am having more success blogging about small arms technology than I ever thought I would.<br />
<br />
The few readers I have will already know that I am now full-time blogging at TheFirearmBlog.com. Instead of posting an article every month here, and accepting a modest check from Google, <a href="http://www.thefirearmblog.com/blog/author/nathaniel-f/">I am blogging full time at TFB,</a> posting thirteen articles per week and covering both big and small topics. I have essentially complete creative control there; there is a considerable degree of separation between the people who pay the bills and those who do the writing. I won't pull the curtain back too much on TFB, but the content you see from me there is what you would get were I posting on my own time here (except I can post much, much more often at TFB, thanks to not having to work as much). When I first started working there, I was concerned that I would be forced to post on topics I did not care about, or that there would be a lot of micro-managing coming from the top. Not only did this not turn out to be the case, but thanks to the paycheck I get there I can buy more books (and I have more time to read them), meaning I am essentially working full time to bring my readers the best writing that I can, informed by both the additional resources at my disposal and by the extra opportunities being a writer there affords me. Indeed, so complete has my control over my content been as a writer for TFB that this blog has remained without update for so long; originally, I planned to continue posting here those articles I felt didn't fit in TFB, or would be too risque to ask the bosses to pay for. So far, it has been the case that <i>no</i> articles I have written proved unsuitable for TFB, and this blog has been all but abandoned as a result.<br />
<br />
Steve asked me once if I enjoyed writing for TFB - he maintains that he wants his writers to enjoy their work. In truth, writing for them has been nothing short of magical for me. I am employed doing what I love (running my mouth - err, fingers), as a result of this I can write articles I never would have been able to without being paid, and I reach an audience that few other history-oriented bloggers do.<br />
<br />
RPM will be updated again - if and when I find something appropriate that does not pass muster at TFB. In the meantime, I'd like to share a few articles I've written that I feel are among my best, as well as my contact information.<br />
<br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/04/02/sturmgewehr-assault-rifle-developments-prior-1942/">Before The Sturmgewehr: Assault Rifle Developments Prior to 1942</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/08/08/energy-dont-sweat/">Energy: Don’t Sweat It!</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/09/19/short-history-tappet-operation/">A Short (Stroke) History of Tappet Operation, Part I: How It Works</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/09/24/firearms-semantics-battle-rifle-assault-rifle/">Firearms Semantics: “Battle Rifle” and “Assault Rifle”</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/09/30/short-history-tappet-operation-part-ii-early-history-tappet-designs/">A Short (Stroke) History of Tappet Operation, Part II: Early Tappet Designs</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/10/06/find-case-capacity-solidworks/">How To Find Case Capacity With SolidWorks</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/10/28/short-stroke-history-tappet-operation-part-iii-m1-carbine-cometh/">A Short (Stroke) History of Tappet Operation, Part III: The M1 Carbine Cometh</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/11/10/usamu-264-usa/">The US Army Marksmanship Unit’s .264 USA</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/11/23/uncommon-shooting-tips-for-beginners/">8 Uncommon Rifle Shooting Tips For Beginners</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/12/13/ten-forgotten-military-rifles/">Ten 20th Century Military Rifles History Has Forgotten</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/12/14/hindsight-is-3006-critique-of-the-m1-garand/">Hindsight Is 30/06: A Critique Of The M1 Garand</a></span><br />
<span style="background-color: white; font-family: Arial, Helvetica, sans-serif; font-size: 14px; line-height: 20px; text-align: center;"><a href="http://www.thefirearmblog.com/blog/2014/12/23/small-arms-technology-really-plateaued/">Small Arms Technology: Has It Really Plateaued?</a></span><br />
<br />
Contact info:<br />
Email: nathaniel.f@staff.thefirearmblog.com<br />
Twitter: @TFB_Nathaniel_F<br />
<br />Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0tag:blogger.com,1999:blog-5557913977913148366.post-68337449755273369552014-05-13T22:17:00.002-07:002014-05-14T17:48:38.715-07:00Are U.S. Soldiers Dying From Inadequate Weapons? No.I dislike doing rebuttal posts. The temptation is strong to adopt a simple quote-and-refute style, which costs little time and allows me to return to my only modestly interesting but very necessary daily life. This style is only compatible with lazy writing, however, and it's bad form to use it too often. Even so, there is a need for a direct response to some works of "journalism" which rely on sensationalist headlines over content to get attention, and which spread falsehoods, misconceptions, and sometimes even outright lies in the process.<br />
<br />
I was asked by a friend what I thought about <a href="http://www.everyjoe.com/2014/05/12/politics/american-soldiers-are-dying-because-of-inadequate-weapons/">this hit piece</a> on the M16/M4 platform and the 5.56mm caliber, which I decided offered me an opportunity to write a little more about the subject. As if anyone felt I hadn't already written enough, that is. Interestingly, the piece was written by Tom Kratman - a name I had to google - who is apparently a veteran of the 5th Special Forces Group and of 19 years in regular Army, eventually retiring at O-5 (the same as my father, of a different branch, coincidentally). He also writes science fiction for Baen, the same publisher where the old THR (a major haunt of mine, once upon a time) moderator Larry Correia now writes.<br />
<br />
Kratman is then no neophyte as a writer or novice to military thinking, but this in my opinion only lends a hue of bafflement to his <a href="http://www.everyjoe.com/author/tomkratman/">two EveryJoe articles.</a> This man was special forces, and an officer, I must keep reminding myself as I read every tired myth, regurgitated piece of gunwriter hype, and mis-remembered factoid.<br />
<br />
It is difficult for me to not be critical of the pieces, both from a factual and a writing standpoint. When my inner monologue reads the figures on my liquid crystal display, I am taken back to caffeine-and-pizza fueled spring mornings and afternoons, sitting in one piece chair-desks intended for the tiny Japanese furniture maker who designed them while listening to a youth who hasn't yet learned to shave the few wisps of a Van Dyke growing on his otherwise newborn face wring out a thin argument he decided on a week before. "Write something we can sell," I wonder if that phrase was ever uttered aloud or transmitted via electrons down copper wires during the planning phase of these two articles. Or perhaps Mr. Kratman truly believes in his premature ideas, which are so poorly supported they are in free-fall, about to reach terminal velocity.<br />
<br />
"Remember, he was in 5th Special Forces Group, and a Lieutenant Colonel," again.<br />
<br />
Let's step back. Many people disagree with me regarding my opinions of the AR-15 rifle family and the 5.56mm cartridge especially. Some of those people, I can hold a discourse with, and present the evidence I have for my position as best I can, to reach a mutual understanding of ideas, experiences, and views which led our opinions to where they are. Some I cannot, because they are too used to fighting the good fight; too zealous for a true mutual discourse.<br />
<br />
Many more are too wrapped up in thin premises fed to them via casual reading of the latest issues of tactical magazines in the Barnes & Noble to really have a decent conversation with. It's this last kind that Mr. Kratman most closely resembles, from his escape-velocity exaggeration of the differences in capability of the M4 carbine and M16 rifle, to his mis-placed snark about the vagueness of the ACR program from the 1980s and 1990s. This last plays off an assumption that isn't true - that the ACR program demanded a deliberately vague "100% improvement" over the M16, begetting the almost laughably inane comment: "That means that we will never have a rifle that’s 99% better." In truth, <a href="https://www.youtube.com/watch?v=KVRyY5QH9Lo&index=18&list=FLnamAXbyUg1naET1N597Zeg">the ACR program's goal was very specific:</a> The winning rifle had to demonstrate a 100% improvement <i>in hit probability</i> during a highly sophisticated course designed specifically to measure that factor with soldiers under combat stress.<br />
<br />
None of the rifles even came close. None of the advanced concepts, not burst fire, not caseless ammunition, not four power optical sights, improved the probability of a hit anywhere close to 100% over the M16A2 rifle. Those design elements that did significantly aid the hit probability - most notably optical sights - were incorporated into future AR-15 pattern service rifles and are in use today. To Mr. Kratman, however, the M4A1 with laser, CCO, vertical grip, and light might as well be an M16A2. The degree to which this is true is irrelevant - A <i>G11</i> might as well be an M16A2 in terms of hit probability, something that Mr. Kratman ignores in favor of the white-noise-esque "they're failing our boys!" drone.<br />
<br />
Kratman rounds out the article with more sophomoric whinging dressed as snark, and an off comment about the French. "A Lieutenant Colonel and veteran of the 5th SFG..." Yes, of course, I mustn't forget.<br />
<br />
His follow up begins by repeating another half-truth about the M16; that the Army never wanted it and it was all McNamara's fault, a "fact" that ignores that the Army agreed to cancel M14 production in favor of the extremely ambitious SPIW, and McNamara was forcing them to, you know, <i>actually provide rifles to the troops</i> in the meantime. It may be presumptuous of me to think that this is something armies are expected to do, but I'll risk it. Eventually, SPIW crashed and burned, and the surprisingly good M16 became the mainstay of the Army for a half-century. None of this matters to Kratman, of course, since it doesn't make for good copy.<br />
<br />
Where some sensationalist gunwriters would take a "back to basics" tack, and suggest re-adopting the M14 in .280 British or some such nonsense, Kratman instead talks about some potential technological improvements that could be in the pipeline for small arms, along with a number of other things that rifle salesmen want you to believe are technological improvements, but actually aren't. His list goes: 1. Intermediate-intermediate calibers, 2. Hyper burst, 3. Carbon-fiber barrels, 4. Electronic ignition, 5. Plastic cased ammunition, 6. Caseless ammunition, 7. A gas piston operating rod, and 8. Optical sights. 2, 3, 4, and 5 fit in with potential technologies that could improve the rifles of the future, 1 and 7 mostly sell rifles, not really offering anything over the 5.56mm cartridge and the AR-15 platform, 6 is all but dead due to technical issues, and 8 has already been implemented, further calcifying my suspicion that Mr. Kratman's technical knowledge of the subject is stuck in 1991.<br />
<br />
What's strange is that he doesn't use this list to paint a rosy picture of the future of small arms in contrast to its oft-claimed stagnation; he uses it (in yet another attempt) to <i>bash the M16.</i> As if, somehow, they could have issued rifles then in 1964 that utilized technologies that are just now maturing to a basic level of feasibility. Some early AR series rifles did trial composite barrels and carbon-fiber handguards, features subsequently deleted in later versions because <i>they didn't work very well then.</i> It's as if Mr. Kratman doesn't understand that just having a working prototype doesn't mean you can make ten million rugged, mature, combat-ready weapons.<br />
<br />
<i>"A Lieutenant Colonel and veteran of the 5th SFG,"</i> I must remind myself.<br />
<br />
It's bizarre to read a piece so sophomoric and poorly researched and constructed, only to follow the authorship trail and read a biography that impressive. Simply put, while I do not demand that everything I read reinforce my own opinions and ideas, I do not expect this sort of thing from a Special Forces Group veteran, much less one who's an O-5 rank and who gets paid to write for a living.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com10tag:blogger.com,1999:blog-5557913977913148366.post-55821370957413770292014-04-20T20:48:00.000-07:002014-04-21T00:12:06.514-07:00On Combat Shooting (Part II)Anthony G. Williams, in his article <i><a href="http://www.quarry.nildram.co.uk/Assault.htm">Assault Rifles And Their Ammunition: History and Prospects</a></i> cites this line from <i><a href="http://usarmy.vo.llnwd.net/e2/c/downloads/215919.pdf">Dual Path Strategy Series: Part III - Soldier Battlefield Effectiveness</a></i> written by the PEO Soldier G5, Strategic Communications Office in August of 2011, to support his idea for a 6.5mm general purpose cartridge (GPC):<br />
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"Ultimately, Army service rifles must be general purpose in nature and embody a series of tradeoffs that balance optimum performance for a wide range of possible missions in a range of operating environments. With global missions taking Soldiers from islands to mountains and jungles to deserts, the Army can’t buy 1.1 million new service rifles every time it’s called upon to operate in a different environment."</blockquote>
However, earlier in that paper is contained this section on the range of the rifleman:<br />
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The maximum effective range of a weapon system is also a key element as it represents the potential for how far out a Soldier can effectively engage the enemy. This is also critical as it affects a Soldier’s ability to leverage an overmatch advantage. Doctrinally, this means that a Soldier will look to engage the enemy at a range that is greater than the range at which they can be engaged by enemy fire (typically 20 percent). According to FM 3-22.9, Rifle Marksmanship M16/M4 Series, there are three ranges of concern. First, there is the detection range, which must be well beyond the effective range of the weapon system. This provides the Soldier time to prepare to engage the enemy at the farthest possible ranges. The next band is the range overmatch distance, whereby friendly Soldiers can engage the enemy, but the enemy cannot engage the Soldiers. The final band is the threat engagement range where enemy personnel can target friendly forces.<br />
<br />
Optimally, friendly forces will engage as the enemy enters the range overmatch area. This advantage is short lived however, since a quickly approaching enemy can move through this area in seconds. For example, according to The Encyclopedia of Land Warfare in the 20th Century, the effective range for AK-47 fired on semi automatic is 400 meters. The effective range for an M4 Carbine is 500 meters. The 100 meter difference provides a decisive range overmatch capability so long as Soldiers are proficient at hitting targets at the 400-500 meter range, which is why extensive marksmanship training is so critical.<br />
<br />
The range of a weapon system relies heavily on the ammunition the weapon fires and the length of the barrel. Systems that utilize 5.56mm ammunition typically cite ranges of 500 – 550 meters for point targets while U.S. weapon systems that fire 7.62x51mm typically cite ranges closer to 800 meters for point targets. The rounds actually travel further but tend to destabilize after they slow to subsonic speeds and therefore lose accuracy. Longer barrels allow more of the propellant's energy to be transferred to the projectile, resulting in greater range. The spiral grooves inside a rifled barrel impart spin to the round. The spin stabilizes the round which provides accuracy, though it doesn’t necessarily increase the average range of the system.<br />
<br />
Regardless of the range potential for certain weapon platforms, the human factor must be considered. Studies have shown that Soldiers can only consistently hit a human-size target more than 300 meters away 50 percent of the time or less on a qualification range. The numbers are significantly lower when a Soldier is operating in high stress environments. </blockquote>
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Therefore, whether a Soldier is firing a 5.56mm system with an effective range of 500 meters, or a 7.62mm platform with an effective range of 800 meters, what really matters is whether he or she has the skill to hit the target to begin with. Taking the human factor into account, one could argue that the “real world” effective range of a 5.56 system is similar to a 7.62mm weapon platform because the range potential of both platforms significantly exceeds the average Soldier’s marksmanship ability. This is not to say that exceptional Soldiers such as U.S. Army Snipers and Squad Designated Marksmen with specialized training are not fully capable of firing small arms to their maximum potential.<br />
<br />
The value of having a system capable of increased range not only depends upon the skill of the operator, but it also depends upon the operating environment. In urban or restrictive terrain, for example, most line-of-sight ranges are significantly less than a weapon’s range potential. In more open terrain, the engagement range increase. For example, according to Lt. Col. Henthorn, in operating environments like Iraq, 80 percent of engagements are less than 200 meters. While in more distributed environments like Afghanistan, only 50 percent of engagements are less than 300 meters. </blockquote>
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What this is essentially saying is that the well-trained rifleman is effective out to 500 meters regardless of the caliber of rifle he is using, even though, in Afghanistan, approximately half of engagements occur beyond 300 meters. Given this, how would issuing GPC-caliber infantry rifles help the rifleman to be more effective?<br />
<br />
The paper goes on to talk more about the general purpose round as they define it. Contrary to what Wr. Williams's citation implies, the author of the paper considers the M855A1 EPR to be a true general purpose cartridge, as it can engage a wide variety of targets reliably within the effective range of the rifle. This indicates that what Mr. Williams and the author of the paper (and, indeed, the US Army) mean by "general purpose" ammunition is different.<br /><br />
Regardless, I recommend that the reader <a href="http://usarmy.vo.llnwd.net/e2/c/downloads/215919.pdf">follow the link</a> and read the whole thing.</div>
Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com2tag:blogger.com,1999:blog-5557913977913148366.post-36015219307722891242014-04-02T21:33:00.001-07:002014-04-02T21:33:37.672-07:00Momentum Has Nothing to Do With Stopping PowerThere is a major misconception that pops up often in discussions of small arms: That momentum reflects in some way the terminal effect that a projectile has on a human target. It seems to be standard in the gun journalism industry when evaluating new calibers for game or war to test them against steel poppers, implying or even outright stating that this informs the terminal effect of the round. Even Larry Vickers, to whom I am not even close in terms of experience, <a href="https://www.youtube.com/watch?feature=player_detailpage&v=0Q8P7IQFb3E#t=1176">says in this video about PDWs</a> that the low momentum produced by the 4.6x30 round - making it unable to knock down the steel target - is a "clue" to low terminal performance.<br /><br />Now, I have little expectation that a 4.6x30 round, which produces about 540J from the MP7, will perform much better against a human target or gel block than a 9mm JHP or even FMJ. It may more consistently perform after penetrating ribs, but in general, the round is limited in its effectiveness by its low muzzle energy, <a href="http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA240295">and its ability to deposit that energy in the target</a> (link starts a download). However, is what Larry says true? Is low momentum a "clue" that a round might not have very good terminal effectiveness? Well, I don't really think so. Sure, a cartridge with marginal terminal effectiveness, like the 4.6x30, might have low linear momentum. However, a cartridge like .45 ACP, which in hardball form produces no greater energy than the 4.6x30, produces more than two and a half times the linear momentum; comparable to the much, much more effective 5.56mm round, in fact.<br /><div>
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Because of all the variables involved in the problem of terminal effectiveness against human targets - including the target's mental state, the perceptions of the shooter, and most important, the location of the hit - it can be difficult to say what is and is not relevant to the total sum of terminal effect. However, momentum is one metric that can be discounted entirely. Consider that when a gun fires, it creates a force going in two directions, the bullet and gas going forward, and the firearm itself going backward. This force acts on both bodies over the same length of time - that is, however long (and a little after, due to muzzle thrust) the bullet is in the barrel. Because the forces pushing the bullet and gas out the barrel, and pushing the gun backwards against the shooter's shoulder are equal and act over the same length of time, the momentum of the sum of the bullet and the gas propelling it, and the rifle recoiling, is the same. This means that the momentum of the rifle recoiling into your shoulder as you fire will always be greater than the momentum of the bullet as it hits the target, for two reasons. First, because the gases escaping from the muzzle account for momentum lost, and because the bullet loses velocity - and thus momentum - as it flies downrange, whereas the rifle doesn't have to travel to recoil into your shoulder.<br /><br />However, we observe as the unspoken first law of shooting that guns have a deadly end, and a non-deadly end. If momentum informed the terminal effect of a weapon against living targets, we'd all be dead fools.<br /><br />So remember, the next time you're shooting silhouette targets with your .45 ACP 1911 and they fall with a satisfying "clunk" to the ground, the only game the momentum of that 230gr hardball ever felled were made of AR500 steel.</div>
Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com8tag:blogger.com,1999:blog-5557913977913148366.post-8071217642113612462014-04-02T20:38:00.001-07:002014-04-21T00:51:31.302-07:00Check me out at The Firearm Blog!About a month and a half ago, I was contacted by Steve of <a href="http://www.thefirearmblog.com/blog/">The Firearm Blog</a> to re-post my article <i><a href="http://196800revolutionsperminute.blogspot.com/2013/11/the-case-against-general-purpose.html">The Case Against A General Purpose Cartridge</a></i> up at his website. After a short conversation, he decided to hire me on as a monthly writer. So far, I've written two articles for them, so my readers <a href="http://www.thefirearmblog.com/blog/author/nathaniel-f/">should go check them out!</a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com1tag:blogger.com,1999:blog-5557913977913148366.post-28854470130331499452014-03-14T17:56:00.001-07:002014-03-14T18:34:53.301-07:00The General Purpose Cartridge RevisitedI've come under some fire on Internet forums for "misrepresenting" the GPC concept as being heavier than it would in actuality. While I feel that the concept in my <a href="http://196800revolutionsperminute.blogspot.com/2013/11/the-case-against-general-purpose.html">The Case Against article</a> - though constrained by several requirements set forth by some members on Mr. Williams' forum - is a perfectly valid approximation, today I hope to address this complaint by creating the absolute lightest GPC estimate I possibly can while still sticking to conventional ammunition design and fulfilling the basic requirement that it not have any less residual energy at 1,000 m than M80 Ball.<br />
<br />
First, I need to recall that M80 produces just over 410 J at that range (.195 G7 BC, 2,750 ft/s muzzle velocity, Army Metro atmospheric conditions). You can see this for yourself if you head over to <a href="http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi">JBM's ballistic calculator</a> and plug in the appropriate values. My GPC must meet or exceed this value. To really get the lightest weight possible, I'm going to need a very good form factor for my bullet- since this is all about retained energy at range. The best form factor I know of for a service projectile is .889 i7, and belongs (paradoxically) to the first spitzer rifle bullet to see service, the French Balle D, an all-brass 12.8 gram boattail projectile with a fairly unique design. If I scale that bullet down to .264" caliber, it weighs just under 7.2 grams.<br />
<br />
Since the Army has spent a bunch of time, money, and effort refining their M855A1 EPR design, it seems unlikely that any new caliber would have a substantially different projectile design. Fortunately, I only need to make moderate changes to the Balle D to accommodate this. The scaled-down projectile will be slightly longer - proportionally - than the original at 33.5mm in length, as well as slightly lighter at 7.0 grams. Now, I can find my ballistic coefficient, which works out to a very impressive .249 G7. Running that through JBM a few times tells me I need a muzzle velocity of 2,800 ft/s to meet M80's energy at a kilometer:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRowfCHbIfvXInnkg-t8t9w3sGo4Wl6hLibzahpl1zsAofvswlTEBID_OAaGGe_o5qmTsIjc8d2TAJ3mL5LGBW1c2cklUiAH8i4OGhb4wi0qDDAmVn7gcMjwajbl2-Gd_jGthI_18n0VpN/s1600/6.5mm+Lightweight+GPC+Trajectory.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRowfCHbIfvXInnkg-t8t9w3sGo4Wl6hLibzahpl1zsAofvswlTEBID_OAaGGe_o5qmTsIjc8d2TAJ3mL5LGBW1c2cklUiAH8i4OGhb4wi0qDDAmVn7gcMjwajbl2-Gd_jGthI_18n0VpN/s1600/6.5mm+Lightweight+GPC+Trajectory.png" /></a></div>
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These are some very impressive ballistics! Now, let's see how much this performer would weigh. To shave as much weight as possible from the design, I am going to use M855A1's peak pressure of 62,000 PSI, as well as the same case taper and shoulder angle of 5.56. Many have argued that 62,000 PSI is too much pressure for a rifle cartridge, and that 5.56's case taper and shoulder angle are a detriment to its reliability in automatic weapons, which is part of the reason why my last estimate was so heavy. This time around, I'm pulling out all the stops; no expense will be spared making this GPC as light as I can. In my opinion, the .5 degrees case taper and 23 degree shoulder of the 5.56mm are adequate, and the 62,000 PSI peak pressure is made safe by more thermally stable propellants. I will move on.</div>
<br />
After doing several run throughs with the <a href="http://kwk.us/powley.html">Powley computer,</a> I found that about 41 grains case capacity was needed to generate the sort of performance I was looking for from 20" barrels (this, as far as I know, being the length of barrel chosen by Mr. Williams as optimum for his GPC). Using Solidworks, I created a fairly svelte case: based on the .30 Remington case head and only 46.4mm long, it has almost exactly 41 grains case capacity:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPeZ3ZKC7uTjZ27lmmkQTaoBAE_v9ulIR4ZWU-rDCTDzKawdPgPbmIk9qQ7iPyZX46GgywCghsVsNCsr73-zfo3Hj8QNNztIHorX3oF5cMjvp2qKYCvOD5b7zrWN-zwHg-Z2Ndp7X5m6Hb/s1600/6.5mm+Lightweight+GPC+Case.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPeZ3ZKC7uTjZ27lmmkQTaoBAE_v9ulIR4ZWU-rDCTDzKawdPgPbmIk9qQ7iPyZX46GgywCghsVsNCsr73-zfo3Hj8QNNztIHorX3oF5cMjvp2qKYCvOD5b7zrWN-zwHg-Z2Ndp7X5m6Hb/s1600/6.5mm+Lightweight+GPC+Case.png" height="640" width="617" /></a></div>
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Here are the Powley results for my completed cartridge:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmoPnsF7Y7qAZ2KSa48Apw785siR9jyz8D7hwuPAn0w4fgKnS0tyQ9lB8D1SnqUXzeI2NCF6W9DThyMeXP4-NzYsXmBT8YlYrOsj_duNdGHJge-JFGg_6RZF93fKkdcVc6lWtX5kpucEx2/s1600/6.5mm+Lightweight+GPC+Powley.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhmoPnsF7Y7qAZ2KSa48Apw785siR9jyz8D7hwuPAn0w4fgKnS0tyQ9lB8D1SnqUXzeI2NCF6W9DThyMeXP4-NzYsXmBT8YlYrOsj_duNdGHJge-JFGg_6RZF93fKkdcVc6lWtX5kpucEx2/s1600/6.5mm+Lightweight+GPC+Powley.png" height="398" width="640" /></a></div>
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Judging by the propellant weights of both the 6.8 SPC and the 6.5 Grendel, though, that 29.1 grain charge weight seems a little light to me. A spit-in-the-wind estimate puts me at 34.7 grains charge, which sounds more reasonable. Now, we can figure out how much the cartridge weighs.</div>
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The bullet, of course, will be 7.00 grams. Large rifle primers weigh about .35 grams, as I mentioned in The Case Against. The charge, in metric, works out to 2.25 grams, and the case itself weighs 7.39 grams if made of brass, or 6.91 grams if made of steel. I will assume steel-cased ammunition, which gives me a total weight of 16.51 grams per cartridge (16.99 grams for brass). 16.5 grams is absolutely fantastic, and lighter even than Mr. Williams' target weight for a GPC with a 7 gram bullet. Let's look at what that means for the infantry platoon:<br />
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Weight of ammunition (only, not including magazines or links) of infantry squad breakdown by squad role: </blockquote>
<blockquote class="tr_bq" style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 13px; line-height: 18.200000762939453px;">
Squad Leader: 210 rounds 5.56mm, totaling 2.54 kg<br />
Team Leader: 210 rounds 5.56mm in magazines, 200 rounds linked 5.56mm for M249 totalling 4.96 kg (x2)<br />
Automatic Rifleman: 800 rounds linked 5.56mm, totaling 9.68 kg (x2)<br />
Grenadier: 210 rounds 5.56mm in magazines, 200 rounds linked 5.56mm for M249 totaling 4.96 kg (x2)<br />
Rifleman: 210 rounds 5.56mm in magazines, 200 rounds linked 5.56mm for M249 totaling 4.96 kg (x2) </blockquote>
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<b>Weight of ammunition of infantry squad: 51.7 kg (x3)</b><span style="background-color: transparent;"> </span></blockquote>
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<b style="background-color: transparent;">Weight of ammunition of infantry squad with 16.5 gram GPC: 70.5 (x3)</b> </blockquote>
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<b>Weight of ammunition of infantry squad with 20 gram GPC: 85.4 kg (x3)</b> </blockquote>
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<b>Weight of ammunition of infantry squad with M240s in place of M249s: 85.5 kg (x3)</b></blockquote>
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Weight of ammunition (only, not including magazines or links) of weapons squad breakdown by squad role: </blockquote>
<blockquote class="tr_bq" style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 13px; line-height: 18.200000762939453px;">
Squad Leader: 210 rounds 5.56mm, totaling 2.54kg<br />
Machine Gunner: 300 rounds linked 7.62mm, totaling 7.26 kg (x2)<br />
Assistant Gunners: 210 rounds 5.56mm in magazines, 400 rounds linked 7.62mm for M240 totaling 12.22 kg (x2)<br />
Ammunition Bearer: 210 rounds 5.56mm in magazines, 300 rounds linked 7.62mm for M240, 140 rounds 7.62mm in magazines totaling 13.2 kg (x2) </blockquote>
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<b>Weight of ammunition of weapons squad: 64.5 kg</b> <span style="background-color: transparent;"> </span></blockquote>
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<b>Weight of ammunition of weapons squad with 16.5 gram GPC: 53.0 kg</b></blockquote>
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<b>Weight of ammunition of weapons squad with 20 gram GPC: 63.8 kg</b></blockquote>
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Weight of ammunition (only, not including magazines or links) of platoon headquarters breakdown by squad role </blockquote>
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Platoon Leader: 210 rounds 5.56mm, totaling 2.54 kg<br />
Platoon Sergeant: 210 rounds 5.56mm, totaling 2.54 kg<br />
Radio Operator: 210 rounds 5.56mm, totaling 2.54 kg<br />
Combat Medic: 210 rounds 5.56mm, totaling 2.54 kg </blockquote>
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<b>Weight of ammunition of platoon headquarters: 10.2 kg</b> <span style="background-color: transparent;"> </span></blockquote>
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<b>Weight of ammunition of platoon headquarters with 16.5 gram GPC: 13.4 kg</b></blockquote>
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<b>Weight of ammunition of platoon headquarters with 20 gram GPC: 16.8 kg</b> </blockquote>
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</blockquote>
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<b>Total weight of ammunition in the platoon: 229.3 kg</b> <span style="background-color: transparent;"> </span></blockquote>
<blockquote class="tr_bq" style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 13px; line-height: 18.200000762939453px;">
<b>Total weight of ammunition in the platoon with 16.5 gram GPC: 277.9 kg</b></blockquote>
<blockquote class="tr_bq" style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 13px; line-height: 18.200000762939453px;">
<b>Total weight of ammunition in the platoon with 20 gram GPC: 336.8 kg</b> </blockquote>
<blockquote class="tr_bq" style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 13px; line-height: 18.200000762939453px;">
<b>Total weight of ammunition in the platoon with M240s in place of M249s: 330.9 kg</b> </blockquote>
<blockquote class="tr_bq" style="background-color: white; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 13px; line-height: 18.200000762939453px;">
<b>Weight increase in the platoon if Carl Gustafs are issued in place of 60mm mortars: 47.5 kg</b></blockquote>
<br />
As my readers can see, even this extremely optimistic estimate still adds almost fifty kilograms of ammunition to the infantry platoon (to say nothing of the increase in weight from the heavier belt links, magazines, and weapons that would be needed to chamber the cartridge). I've heard some GPC proponents claim that the savings in weight of a GPC vs. 7.62mm would balance out its increased weight vs. 5.56mm weapons at the platoon level; this is clearly not true. <b>The GPC - even the lightest possible GPC - represents a significant weight increase for the infantry rifle platoon</b> (or a corresponding reduction in rounds carried). Further, even replacing the platoon's 60mm mortars with direct-fire recoilless rifles is lighter than switching whole hog to the GPC. <a href="http://www.foxnews.com/us/2014/03/11/big-guns-army-soldiers-to-get-powerful-new-swedish-made-tank-stopper/">The Army has already decided to introduce Carl Gustafs to the infantry,</a> which in my mind neatly solves the issue of having to call in air or artillery support when under fire from long-range Taliban ambushes; this being the primary rationale for the GPC in the first place. If the mortars are left home, American soldiers will be able to project high explosive firepower at long ranges without the need for an expensive and time consuming ammunition change-over, and with no more additional burden at the platoon level than would result from fielding a GPC.<br />
<br />
This cartridge I've designed is an impressive ballistic hot rod. It would make some sense for 7.62mm weapons to be replaced with weapons in a similar caliber, retaining the capability of that round while slashing the weight of ammunition by about 30%. I felt much the same in my initial article about my 20 gram GPC estimate. Anything that reduces the soldier's load without reducing capability or introducing problems is probably worth doing, if you can afford it. What I disagree with is the idea that a cartridge such as this should be a general purpose cartridge; that it should be issued to riflemen as well as designated marksmen, machine gunners, and as ammunition for static machine guns. The additional weight of ammunition and rifles, and increased recoil and size, sours the idea considerably in my mind vs. the two caliber system.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com24tag:blogger.com,1999:blog-5557913977913148366.post-70554853946353345792014-03-13T15:02:00.003-07:002014-03-13T15:03:16.543-07:00Called It!I don't normally reblog without commentary, but it seems my earlier notion that the Carl Gustav could be issued in the general Army as a way to improve infantry effectiveness at long range <a href="http://www.foxnews.com/us/2014/03/11/big-guns-army-soldiers-to-get-powerful-new-swedish-made-tank-stopper/">has proven prescient.</a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0tag:blogger.com,1999:blog-5557913977913148366.post-56998618801685673202014-03-10T09:18:00.001-07:002014-03-10T09:23:46.459-07:00.300 AAC Blackout: The End of 5.56?<a href="http://300aacblackout.com/resources/300-BLK.pdf">This PDF from Advanced Armament Corp</a> extolling the virtues of the .300 AAC Blackout vs. 5.56mm includes a curious section:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUcBZng610YadiLgw3tawisbeNmKUAU36f2YPETE4cktpyid2oPeZsAkcI4_aPhgozLiJ-TS3ivMlJBgaXMOYronSmcha9yqCryypWcIllknCjjc4q8GnpSWxQhFfCf3YLk7YY2JIZYlyG/s1600/300blackoutwhat.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUcBZng610YadiLgw3tawisbeNmKUAU36f2YPETE4cktpyid2oPeZsAkcI4_aPhgozLiJ-TS3ivMlJBgaXMOYronSmcha9yqCryypWcIllknCjjc4q8GnpSWxQhFfCf3YLk7YY2JIZYlyG/s1600/300blackoutwhat.png" height="480" width="640" /></a></div>
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Boy those sure are some impressive numbers for an overgrown .30 Carbine! Do they reflect reality, though? Let's check JBM's ballistic calculator. First, we'll need to find a ballistic coefficient figure that reflects a 125gr .300 Blackout load. <a href="http://www.midwayusa.com/product/1482899294/sierra-matchking-bullets-300-aac-blackout-308-diameter-125-grain-hollow-point-match">Here's a very impressive looking Sierra 125gr Matchking,</a> but it's BC is in G1, not G7 like we want. Fortunately for us, <a href="http://www.jbmballistics.com/cgi-bin/jbmgf-5.1.cgi">JBM has a drag function converter.</a> Using this, we get a G7 ballistic coefficient at 2,220 ft/s of .170. Now we can plug all this into <a href="http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi">JBM's trajectory calculator</a> to see if AAC's claims are accurate. For this, we'll leave energy in ft-lbs, but change range to be in meters:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglbtW-s7iEYA4jDchImvGsbWAH-TUsKSc3xPMQnwiwoZs_tcJ7FkReeDJgmHz6Vq2asGDW_W4AuuqL250JLpKBfPulf5S5dT_9Cn6JgUVPBTy_iBQTEt6PEwfOGxi81WSGAP2Q9Ir_XdFo/s1600/300blackouttrajectory.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglbtW-s7iEYA4jDchImvGsbWAH-TUsKSc3xPMQnwiwoZs_tcJ7FkReeDJgmHz6Vq2asGDW_W4AuuqL250JLpKBfPulf5S5dT_9Cn6JgUVPBTy_iBQTEt6PEwfOGxi81WSGAP2Q9Ir_XdFo/s1600/300blackouttrajectory.png" /></a></div>
<div style="text-align: left;">
<br /></div>
<div style="text-align: left;">
That's... Pretty much right on the money for AAC's claims. What about their numbers for 5.56mm?</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjej7BVITnk_sdAfNgh0wlD9-vDYgRjK9nC-3s_ch4q3tsyRoJEB_PLR9by3NN3wFIt6xFKy0UCe0oaaUFxQ1aHp7w3LHWXkAWrFH3BClaU6FnNbY_KVup3CX_D53gyw-FMADt5F4rv7MB0/s1600/5.56accordingtoAAC.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjej7BVITnk_sdAfNgh0wlD9-vDYgRjK9nC-3s_ch4q3tsyRoJEB_PLR9by3NN3wFIt6xFKy0UCe0oaaUFxQ1aHp7w3LHWXkAWrFH3BClaU6FnNbY_KVup3CX_D53gyw-FMADt5F4rv7MB0/s1600/5.56accordingtoAAC.png" /></a></div>
<div style="text-align: left;">
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Not even close, for trajectory.<br />
<br />
Reevaluating this, if we take 5.56's performance at 500m as a baseline for "maximum effective range", then it out-ranges .300 AAC Blackout by about 110m. Further, it's worth noting that at 250m, 5.56 has less than a quarter of the drop, thanks to its laser-like trajectory, which enables <a href="http://www.ar15.com/content/page.html?id=208">the 25 yard combat zero.</a> Worse, 5.56 actually generates slightly more energy per pound than the 125gr .300 AAC Blackout, with 23.8 ft-lbs/gram, vs. 22.7 ft-lbs/gram (how about <i>those</i> units? Working in firearms sure is fun!). It's also worth remembering that <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/705381.pdf">larger FMJs tumble less readily than smaller ones</a> and will deposit less of their energy into a human target, something I can't seem to repeat often enough.</div>
<div style="text-align: left;">
<br /></div>
<div style="text-align: left;">
So does all this make the .300 AAC Blackout a bad cartridge? No, I don't think so. It seems like an interesting concept, being able to switch from a quiet subsonic cartridge to a harder-hitting and longer-ranged supersonic one without changing any hardware other than the magazine. Of course, the high speed low drag types in my audience will have to tell me whether that sort of concept is attractive to anyone other than readers of <i>Tactical Life</i> magazine, but it's certainly still worth looking at.<br />
<br />
What this <i>does</i> remind us is to trust but verify any data you see in a manufacturer's pamphlet or public materials. In this case, it really does seem like AAC had no problem "massaging" the numbers to make their cartridge look better than it really is.</div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUcBZng610YadiLgw3tawisbeNmKUAU36f2YPETE4cktpyid2oPeZsAkcI4_aPhgozLiJ-TS3ivMlJBgaXMOYronSmcha9yqCryypWcIllknCjjc4q8GnpSWxQhFfCf3YLk7YY2JIZYlyG/s1600/300blackoutwhat.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br /></a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com2tag:blogger.com,1999:blog-5557913977913148366.post-26411632205865813472014-02-25T11:24:00.004-08:002014-03-02T23:17:44.999-08:00On Long Range Combat ShootingSeveral times on Internet fora I have been challenged for a "discrepancy" in my position on small arms ballistics, that my claims of having shot man sized targets with 5.56mm weapons out to 900 yards didn't mesh with my assertion that infantrymen are going to have a very, very difficult time hitting anything beyond 500 meters. I've responded to this in various ways over the years (something I've found difficult, never having given military service myself), but here's Chris Hernandez on the matter (H/T, <a href="http://weaponsman.com/?p=14073">Weaponsman</a>):<br />
<blockquote class="tr_bq">
Second thing: For most modern combat, 300 meters is plenty far. I carried an M14EBR (Enhanced Battle Rifle) in Afghanistan, and I could consistently hit a torso-sized rock at 900 meters – at the range, with perfect weather conditions, a good firing position, on a stationary target at a known distance. In combat, with extreme heat or cold, unknown distances, hasty firing positions, adrenaline and moving targets, plus little annoyances like incoming fire, I would have been ecstatic to smoke a mofo at 200 meters.</blockquote>
Every now and again, the stars will align, and a (usually very good) shooter will get a chance to hit targets in combat beyond 500 meters, but this is very rare. Even so, <a href="http://www.youtube.com/watch?v=BDoX8UnQ4D0">specialized 5.56mm ammunition seems to perform decently at these ranges.</a><br />
<br />
Go forth and <a href="http://www.thenewrifleman.com/a-primer-on-optics-an-intro-guide-by-chris-hernandez/">read the whole article (which is about optics selection).</a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com1tag:blogger.com,1999:blog-5557913977913148366.post-73871253267383347082014-02-10T08:17:00.001-08:002014-03-02T23:28:57.250-08:00Accurate Barrel Life Calculator<a href="https://sites.google.com/site/gunresearchattachments/barrel_life_calculator%5B1%5D.xlsm?attredirects=0&d=1">Here's a barrel life calculator I picked up while in school.</a> It estimates the useful barrel life of a cartridge, given the input parameters.<br />
<br />
A few examples:<br />
<div>
<br /></div>
<div>
M855:</div>
<table border="0" cellspacing="0" cols="3" frame="VOID" rules="NONE">
<colgroup><col width="62"></col><col width="201"></col><col width="64"></col></colgroup>
<tbody>
<tr>
<td align="LEFT" height="24" sdnum="1033;1033;General" valign="BOTTOM" width="62"><br /></td>
<td align="CENTER" colspan="2" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="MIDDLE" width="265"><b><span style="font-size: medium;"> Accurate Barrel Life </span></b></td>
</tr>
<tr>
<td align="LEFT" height="21" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000; border-top: 3px solid #000000;" valign="BOTTOM">Bullet dia [in] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="0.223" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="BOTTOM">0.223</td>
</tr>
<tr>
<td align="LEFT" height="20" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="BOTTOM">Loaded Powder [gr] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="25.2" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">25.2</td>
</tr>
<tr>
<td align="LEFT" height="21" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="BOTTOM">Powder heat potential [KJ/Kg] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="3880" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">3880</td>
</tr>
<tr>
<td align="LEFT" height="23" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="MIDDLE">Pressure [Psi] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="55000" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">58000</td>
</tr>
<tr>
<td align="LEFT" height="19" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;1033;General" style="border-left: 3px solid #000000;" valign="MIDDLE">Moly Coating [Y/N]</td>
<td align="CENTER" sdnum="1033;1033;General" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="MIDDLE">n</td>
</tr>
<tr>
<td align="LEFT" height="23" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0_);_(* \(#,##0\);_(* "-"_);_(@_)" style="border-left: 3px solid #000000; border-right: 3px solid #000000;" valign="MIDDLE">Total </td>
<td align="CENTER" bgcolor="#FFFF99" sdnum="1033;1033;0" sdval="3158.05896936652" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="MIDDLE"><b>3049</b></td>
</tr>
</tbody>
</table>
<br />
M80:<br />
<div>
<table border="0" cellspacing="0" cols="3" frame="VOID" rules="NONE">
<colgroup><col width="62"></col><col width="201"></col><col width="64"></col></colgroup>
<tbody>
<tr>
<td align="LEFT" height="24" sdnum="1033;1033;General" valign="BOTTOM" width="62"><br /></td>
<td align="CENTER" colspan="2" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="MIDDLE" width="265"><b><span style="font-size: medium;"> Accurate Barrel Life </span></b></td>
</tr>
<tr>
<td align="LEFT" height="21" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000; border-top: 3px solid #000000;" valign="BOTTOM">Bullet dia [in] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="0.308" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="BOTTOM">0.308</td>
</tr>
<tr>
<td align="LEFT" height="20" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="BOTTOM">Loaded Powder [gr] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="46" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">46</td>
</tr>
<tr>
<td align="LEFT" height="21" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="BOTTOM">Powder heat potential [KJ/Kg] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="3990" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">3990</td>
</tr>
<tr>
<td align="LEFT" height="23" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="MIDDLE">Pressure [Psi] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="62000" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">62000</td>
</tr>
<tr>
<td align="LEFT" height="19" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;1033;General" style="border-left: 3px solid #000000;" valign="MIDDLE">Moly Coating [Y/N]</td>
<td align="CENTER" sdnum="1033;1033;General" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="MIDDLE">n</td>
</tr>
<tr>
<td align="LEFT" height="23" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0_);_(* \(#,##0\);_(* "-"_);_(@_)" style="border-left: 3px solid #000000; border-right: 3px solid #000000;" valign="MIDDLE">Total </td>
<td align="CENTER" bgcolor="#FFFF99" sdnum="1033;1033;0" sdval="2660.44458124463" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="MIDDLE"><b>2660</b></td>
</tr>
</tbody>
</table>
<br />
6.5/8/800:<br />
<table border="0" cellspacing="0" cols="3" frame="VOID" rules="NONE">
<colgroup><col width="62"></col><col width="201"></col><col width="64"></col></colgroup>
<tbody>
<tr>
<td align="LEFT" height="24" sdnum="1033;1033;General" valign="BOTTOM" width="62"><br /></td>
<td align="CENTER" colspan="2" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="MIDDLE" width="265"><b><span style="font-size: medium;"> Accurate Barrel Life </span></b></td>
</tr>
<tr>
<td align="LEFT" height="21" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000; border-top: 3px solid #000000;" valign="BOTTOM">Bullet dia [in] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="0.264" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="BOTTOM">0.264</td>
</tr>
<tr>
<td align="LEFT" height="20" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="BOTTOM">Loaded Powder [gr] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="36.3" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">36.3</td>
</tr>
<tr>
<td align="LEFT" height="21" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="BOTTOM">Powder heat potential [KJ/Kg] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="3890" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">3890</td>
</tr>
<tr>
<td align="LEFT" height="23" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0.00_);_(* \(#,##0.00\);_(* "-"??_);_(@_)" style="border-left: 3px solid #000000;" valign="MIDDLE">Pressure [Psi] </td>
<td align="RIGHT" sdnum="1033;1033;General" sdval="55000" style="border-bottom: 1px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="BOTTOM">55000</td>
</tr>
<tr>
<td align="LEFT" height="19" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;1033;General" style="border-left: 3px solid #000000;" valign="MIDDLE">Moly Coating [Y/N]</td>
<td align="CENTER" sdnum="1033;1033;General" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 1px solid #000000;" valign="MIDDLE">n</td>
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<tr>
<td align="LEFT" height="23" sdnum="1033;1033;General" valign="BOTTOM"><br /></td>
<td align="LEFT" bgcolor="#99CCFF" sdnum="1033;0;_(* #,##0_);_(* \(#,##0\);_(* "-"_);_(@_)" style="border-left: 3px solid #000000; border-right: 3px solid #000000;" valign="MIDDLE">Total </td>
<td align="CENTER" bgcolor="#FFFF99" sdnum="1033;1033;0" sdval="2951.31077428238" style="border-bottom: 3px solid #000000; border-left: 3px solid #000000; border-right: 3px solid #000000; border-top: 3px solid #000000;" valign="MIDDLE"><b>2951</b></td></tr>
</tbody></table>
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It's important to note that this calculator is most useful for precision shooting, but I think in general the results can be multiplied by about 5 to gain an idea of the useful military life of a barrel. Of course, numerous factors influence how toasty a cartridge is to a barrel, including what the barrel's made of, how high the flame temperature of the powder is, and how the bullet is constructed, so this value should only be used to give the user an idea of how much their design will aggravate these factors.</div>
Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com2tag:blogger.com,1999:blog-5557913977913148366.post-78984913045256501272014-02-10T07:56:00.002-08:002014-03-15T10:56:38.622-07:00Comparing 85gr TSX 6.8mm to 5.56At the request of commenter <a href="http://mcthag.blogspot.com/">Angus McThag,</a> I will do a (short) comparison of the 6.8 SPC loaded with the 85gr Barnes TSX to simulated M855 and M193 loads. I already whipped up a simulated M855 load in <a href="http://196800revolutionsperminute.blogspot.com/2014/01/all-your-drop-in-556-replacements-suck.html">my previous post about 5.56 replacements,</a> and I will be referring to that regularly through this article, instead of duplicating the information here. In addition, I will not be using Solidworks models for this estimate, as a reasonable estimate can be attained without doing so.<br />
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In order to make the comparison as even as possible, I need to create a Powley computer performance estimate. While using the Powley computer may not necessarily give the most accurate numbers in terms of performance for a given cartridge, it does provide the most even basis I know of for comparison. In this case, our 85gr 6.8 SPC provides a somewhat sedate 2,770 ft/s with an 85gr bullet:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUWaGX8HvBAg_VhA7oOLOFmOwj2rDJE9GtjPJ27AHhPMLz00bnpoXMEQHLx-sOSo2HHezChHZrB-iu6UjrtvUWhKi4uy4epcXBsdLSTjkBqGP7J3kVjvjWwZ9VgUqVx7d1S22FPS_ufwIb/s1600/85grtsxpowley.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUWaGX8HvBAg_VhA7oOLOFmOwj2rDJE9GtjPJ27AHhPMLz00bnpoXMEQHLx-sOSo2HHezChHZrB-iu6UjrtvUWhKi4uy4epcXBsdLSTjkBqGP7J3kVjvjWwZ9VgUqVx7d1S22FPS_ufwIb/s1600/85grtsxpowley.png" height="368" width="640" /></a></div>
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As you can see, the peak pressure in this example is only 55,000 PSI, vs. the 58,000 PSI used in my last comparison. It is lower because 55,000 PSI is <a href="http://www.ar15.com/content/page.html?id=216">the maximum average pressure of 6.8 SPC according to SAAMI.</a> If 58,000 PSI is used, the cartridge gains about 30 ft/s. The value of 2,770 ft/s sounded a bit low to me, and I thought maybe the Powley computer was giving me an incorrect result. However, when I adjusted the barrel length to 24" and checked it against <a href="http://data.hodgdon.com/main_menu.asp">Hodgdon's reloading data,</a> I found that it was only about 41 ft/s lower than their value. 41 ft/s is definitely enough to make a difference in the performance of a cartridge, but it doesn't imply some kind of error in the computer itself (individual shots can often vary by more than 40 ft/s). For the same of comparison, I will continue to use the 2,770 ft/s value, instead of adjusting it, while noting that real-world values may be slightly higher.</div>
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Plugging this into JBM Ballistics' calculator, we get this (<a href="http://196800revolutionsperminute.blogspot.com/2012/11/where-do-i-get-my-ballistic-coefficient.html">G7 BC is from here</a>):</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9gKFsGGd8DEke7jGOZLDmuqJ05kAVfurnZuQtfcGnj9HvT4fwiV95r6xoXlbjxmG5ROnU6cvlhyphenhyphen4pm23jeypOch2mhmYK7rOvKCo_6WXAxh53RU71ooQhzl1D8ygMt13bcA8czuiZPcD0/s1600/85grtsxjbm.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9gKFsGGd8DEke7jGOZLDmuqJ05kAVfurnZuQtfcGnj9HvT4fwiV95r6xoXlbjxmG5ROnU6cvlhyphenhyphen4pm23jeypOch2mhmYK7rOvKCo_6WXAxh53RU71ooQhzl1D8ygMt13bcA8czuiZPcD0/s1600/85grtsxjbm.png" /></a></div>
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Just over 300 J at 500m? Jeeze, that's not that great. As we found in my last post on the subject, M855 produces over 400 J at that same range. Well, OK, but which cartridge weighs more? Your first clue is the weight of their respective bullets. Having not rendered 6.8 SPC in Solidworks yet, I can't give you an exact figure, but using the weight from <a href="http://www.ar15.com/content/page.html?id=216">the 6.8 Tech Information page</a> I linked earlier of 28 rounds of ammunition, I estimate that the 85gr 6.8 SPC loading would weigh over 15 grams. Given this, it compares pretty unfavorably to M855, producing only 20.5 J/g at 500m, compared to 35.5 for 5.56.</div>
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Why is this value so low? The 85gr TSX is a flat-based bullet, with a poor form factor. It's also pretty light for caliber, and has a fairly low sectional density (about the same as 55gr 5.56)). In light of that, maybe we should compare it to M193:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcjkSDFEdV9EwX9gu0cb-BIA844pDaKDxzb2eo5wcgePbhW01u0vU5AecvDxAlr2w3LDSuv2jKuDPEFmXRcFvLmTBMpFj4tOwZJephOcqbhJptFBug3s0PT6TMjumjrDAKccAtqwTL_JNx/s1600/M193Powley2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcjkSDFEdV9EwX9gu0cb-BIA844pDaKDxzb2eo5wcgePbhW01u0vU5AecvDxAlr2w3LDSuv2jKuDPEFmXRcFvLmTBMpFj4tOwZJephOcqbhJptFBug3s0PT6TMjumjrDAKccAtqwTL_JNx/s1600/M193Powley2.png" height="345" width="640" /></a><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEju-kPFlhfLBg5Bze8rEHokubYacExMIeoDSKelwGiUfdVtqFNYI5EyFIy_GqS4Mc1nskAE5Hd_6AGvnSc9Mupp6h3Z0U5voBuzOXt4oc2g4u8L5XOLaW7-UXVvritLjzDoSkseT3JxhzrP/s1600/M193powley.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEju-kPFlhfLBg5Bze8rEHokubYacExMIeoDSKelwGiUfdVtqFNYI5EyFIy_GqS4Mc1nskAE5Hd_6AGvnSc9Mupp6h3Z0U5voBuzOXt4oc2g4u8L5XOLaW7-UXVvritLjzDoSkseT3JxhzrP/s1600/M193powley.png" /></a></div>
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It only provides 4% more energy at 500m. That's... Rather disappointing. We know that M193 has a cartridge weight of 11.5g, giving it approximately 25.9 J/g at 500m, a full 26% better than the 85gr TSX 6.8. The TSX definitely has the edge in bullet design from a terminal effects standpoint, but those ballistic results simply aren't very impressive.</div>
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I don't think I'm very happy with this result. On the chance that the 2,770 ft/s figure is just <i>too low,</i> I tried to dig up the absolute best performance figures I could for the 85gr TSX, and see how they compared to my Powley estimate for M855. I didn't find much, but I did find <a href="https://www.lwrci.com/articles/SGNLWRCsix8.pdf">David Fortier's article on LWRC's Six8 UICW and its special ATK-made 90gr Gold Dot ammunition.</a> Close enough, I think. To get some sort of performance baseline, I did a little math and got an estimated value of 2,940 ft/s from a 14.5" barrel for the 85gr TSX (this is essentially estimating if you pulled the bullet on an ATK 90gr Gold Dot, and reloaded the case, powder and all, with an 85gr TSX, and then fired it from a 14.5" barrel. Of course, this assumes that the values in the article are correct, and I suspect they're a bit optimistic.). Now we're talking. At 500m, this is what it does:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi611sMO7cvg7Nv_kKOw5lt5Pw2bPVMJhXZ4CwKBNqvc2HuoLhv8TkAu9DNjolvGqVVvZzQFdsD80vnuCupkZJLQe0ftN84Bg1Qgg09lkYuEhTCFN-KeZGm-QjzQsKMpUut1pJ_j2XRYwwK/s1600/85grtsxjbmATKhighpressure.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi611sMO7cvg7Nv_kKOw5lt5Pw2bPVMJhXZ4CwKBNqvc2HuoLhv8TkAu9DNjolvGqVVvZzQFdsD80vnuCupkZJLQe0ftN84Bg1Qgg09lkYuEhTCFN-KeZGm-QjzQsKMpUut1pJ_j2XRYwwK/s1600/85grtsxjbmATKhighpressure.png" height="640" width="466" /></a></div>
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It gains almost 60 J at range from the extra 170 ft/s muzzle velocity, but it still doesn't compare very well to either 5.56, producing only 24.3 J/g at 500m. That's not great performance for a "best case scenario" of the lightweight 6.8mms.</div>
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This article illustrates most clearly to me the value of high form factor, long ogive bullets. At the muzzle, the 6.8mm with lightweight bullets looks fairly impressive, but the poor form factors of those bullets really let it down after a half-kilometer. Even by 300m, the initial estimate for the TSX has fallen below M855 in terms of absolute energy, not to mention energy per pound. The 6.8mm cartridge leaves even less space than 5.56 for long ogive, slender bullets, and I think this is the key to understanding its fairly lackluster performance with low sectional density bullets.</div>
Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0tag:blogger.com,1999:blog-5557913977913148366.post-84552655471489753502014-02-10T03:54:00.005-08:002014-02-10T03:55:30.627-08:00How to remove and replace your Vz. 58's fire control group<h3>
<b>This article was originally posted on another blog of mine in late 2010, but its content is more appropriate here, I think.</b></h3>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUXlnNcr8hRzW36jX5sGK68JeflflYZ5eY_kvADQGRAK1WKgIeiTdF-JUvQJ7waCXsY_j4BB58gLM2S2d5q80qXUXxdnONwYfmx-J-70rvlF8wm2aDLYThModdssj6cGty26IR1nH1q9dY/s1600/P1080007.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUXlnNcr8hRzW36jX5sGK68JeflflYZ5eY_kvADQGRAK1WKgIeiTdF-JUvQJ7waCXsY_j4BB58gLM2S2d5q80qXUXxdnONwYfmx-J-70rvlF8wm2aDLYThModdssj6cGty26IR1nH1q9dY/s320/P1080007.JPG" height="180" width="320" /></a></div>
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I'm going to deviate a little bit from the established nature of this blog, simply because I like to play Good Samaritan every so often and actually add useful content to the Internets.<br />
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You see, recently, I purchased a Vz. 58 steel trigger, to replace the plastic trigger my CZ-USA Vz. 58 came with. When I looked on the Internet for info on how to muck around inside the receiver, I found nothing, so I had to figure it out myself. Trying to remove the fire control group from this rifle without knowing how is really hard, and results in lots of unnecessary scrapes on your receiver, and a lot of fruitless banging and frustration. Removing the FCG after you know what to do, however, is really quite easy, if a bit tricky. I decided to write this to help people do it the easy way.<br />
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The parts can get a bit confusing. I use the same terminology Czechpoint does, and you can find a nearly complete parts list for the Vz. 58 at their website:<br />
http://www.czechpoint-usa.com/products/spare-parts-and-accessories/vz-58-parts-and-accessories/<br />
The title is not so much an accurate description of the content as it is all the search terms I used in trying to find info about how to perform surgery on my Vz.<br />
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Let's begin.<br />
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Firstly, and most importantly, you want to remove the magazine and clear the chamber.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEik99YvkUbJ_4SmKh6Jo1-duxOChHqkrWxUPlquxwZfo2NIzhY3SqV6Upv3BRc3ma0laK1BCKmW1lJ-Tk6MMf8l3_SWGd7Iakuu87ZQvBmXnlAccMRnNn6mz3qhIYyGLOA1CwZGsiQuof5M/s1600/P1080010.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEik99YvkUbJ_4SmKh6Jo1-duxOChHqkrWxUPlquxwZfo2NIzhY3SqV6Upv3BRc3ma0laK1BCKmW1lJ-Tk6MMf8l3_SWGd7Iakuu87ZQvBmXnlAccMRnNn6mz3qhIYyGLOA1CwZGsiQuof5M/s320/P1080010.JPG" height="180" width="320" /></a></div>
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Then, and this is why that last step was so important, you want to flick the safety off if it wasn't already, and pull the trigger.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg75FPAZkb0-ApRd3bEajbkTziJEfyWQcNtsD_N-wqLEWKxct5bZmv7PjPemgXkIvhWIcKMHeH8w7cH7mPk09gG4uIqOhd5ZAfGarL2OybdiQihGrvXnVY55XmEY44A29Q0fih1IeDxCMQe/s1600/P1080021.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg75FPAZkb0-ApRd3bEajbkTziJEfyWQcNtsD_N-wqLEWKxct5bZmv7PjPemgXkIvhWIcKMHeH8w7cH7mPk09gG4uIqOhd5ZAfGarL2OybdiQihGrvXnVY55XmEY44A29Q0fih1IeDxCMQe/s320/P1080021.JPG" height="180" width="320" /></a></div>
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If you followed step one, you should get a click. If you didn't, you should get temporary hearing loss and a hole in something.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjD4-NFCPWdt2GY499m16prRVWu7EFK-5NM-a0iT1N1S15eaBBuQfXn2I0IB0qL_C-Yk6zgqKAbDw35hOQEg0_2FGC08i5ejSBtMtnaG-wwlMHosvyuzZ7N8ubPsNCxW6Mj23QM7370v1Mh/s1600/P1080022.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjD4-NFCPWdt2GY499m16prRVWu7EFK-5NM-a0iT1N1S15eaBBuQfXn2I0IB0qL_C-Yk6zgqKAbDw35hOQEg0_2FGC08i5ejSBtMtnaG-wwlMHosvyuzZ7N8ubPsNCxW6Mj23QM7370v1Mh/s320/P1080022.JPG" height="180" width="320" /></a></div>
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Now, push out the receiver cover retaining pin. This pin likes to push out most of the way and leave about a fifth of itself still retaining the cover, so make sure it's all the way out. If you have difficulty removing the cover, this is almost certainly the problem.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKqtD8_tN0CJOsahzo4dY1DcwJvy_jpH3wfTunc-0FgCG9dedOhmF1_6IXxO_cEJIYt8jBIoof4aQFKuODWp2v1EnVIJS3gckvKQ8_7xisT4O_8IcKLs9fL4FWJW4CUKSPhUc6_CgMAJOw/s1600/P1080023.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKqtD8_tN0CJOsahzo4dY1DcwJvy_jpH3wfTunc-0FgCG9dedOhmF1_6IXxO_cEJIYt8jBIoof4aQFKuODWp2v1EnVIJS3gckvKQ8_7xisT4O_8IcKLs9fL4FWJW4CUKSPhUc6_CgMAJOw/s320/P1080023.JPG" height="180" width="320" /></a></div>
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Next, remove the receiver cover by pushing it forward from the rear, and lifting it up. It should come straight on out. Note the dual captive springs; it's important to line them up properly during reassembly.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhClu2yb-hR1VQPSsZn7ecPtX-gXUO6uxoCd9wAqyJCHzqUVQGhTXVMv38Q0S487gTcgI3AFPM_ntpChA1oAysL_AdM9kew-yGt8kk9Iy8jOiTEMB2xmsWCHaPEo7Mmpi_dDDawueoubQ9A/s1600/P1080024.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhClu2yb-hR1VQPSsZn7ecPtX-gXUO6uxoCd9wAqyJCHzqUVQGhTXVMv38Q0S487gTcgI3AFPM_ntpChA1oAysL_AdM9kew-yGt8kk9Iy8jOiTEMB2xmsWCHaPEo7Mmpi_dDDawueoubQ9A/s320/P1080024.JPG" height="180" width="320" /></a></div>
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Now, remove the bolt carrier assembly by retracting it all the way to the rear, and removing it from the top.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsDRsA3L6m0ivG7p0mpolhvMevo8cWvIJ3fyOOnTwz-zFLnP8mpMI-6kJl8QzRxE_iU3HP4lxMfQg900VxqErwdG5cxTWwPSvGWy-H8_3-KkU15757NnAvFdvqnUV5z3kYFUHXu0C6oyQx/s1600/P1080025.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsDRsA3L6m0ivG7p0mpolhvMevo8cWvIJ3fyOOnTwz-zFLnP8mpMI-6kJl8QzRxE_iU3HP4lxMfQg900VxqErwdG5cxTWwPSvGWy-H8_3-KkU15757NnAvFdvqnUV5z3kYFUHXu0C6oyQx/s320/P1080025.JPG" height="180" width="320" /></a></div>
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Finally, you can inspect the glory that is the Vz. 58 fire control group. When I first tried to remove the old trigger, I just banged on the trigger axis pin until I destroyed two pulled 7.62x54R bullets and gave up that approach. It turns out, the Czechs thought of their trigger axis and sear axis pins backing out and put in two little e-clips.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXh_U5TChDGlCpsa0ZLfxxg7Pxjw0yrjNABPxH_n_KGhjoAGhrj7sxrdl7HUMvUN-mEk4cE_x_T12pR36rm876pK-ccbSDNB8N2zwjbF6RboYSFi5xVKJnjGyPTS7UOD6NQA2uyLg-00mm/s1600/P1080034.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXh_U5TChDGlCpsa0ZLfxxg7Pxjw0yrjNABPxH_n_KGhjoAGhrj7sxrdl7HUMvUN-mEk4cE_x_T12pR36rm876pK-ccbSDNB8N2zwjbF6RboYSFi5xVKJnjGyPTS7UOD6NQA2uyLg-00mm/s320/P1080034.JPG" height="180" width="320" /></a></div>
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These e-clips hold the pins in despite the application of considerable hammering. These e-clips are simple to remove, but for God's sake do not lose them. Just take a screwdriver, or other fine implement, and flick them out. They come off readily.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhL29Q8iy39w1ka6IgFtDsdxy4WAX73ejapjF5JYx6kzx00wSBAFRkM-gPdYaR9GlwTuxz-_LiAz5Kj2oSelceTisk557RsrIfxvPveeiN1hwOHupqVO9Bd088ADyOUFiceecPgWmleqD7F/s1600/P1080026.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhL29Q8iy39w1ka6IgFtDsdxy4WAX73ejapjF5JYx6kzx00wSBAFRkM-gPdYaR9GlwTuxz-_LiAz5Kj2oSelceTisk557RsrIfxvPveeiN1hwOHupqVO9Bd088ADyOUFiceecPgWmleqD7F/s320/P1080026.JPG" height="180" width="320" /></a></div>
<br />
Once both e-clips for the sear and trigger pins are off, tap the two pins out slightly from the left to the right. Tap the sear pin out first, then the trigger pin. Once they come out about a millimeter, there's enough space for you pull them out all the way with a screwdriver or your fingernails. They shouldn't fit tightly.<br />
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It'll take a little finagling, but it should be pretty easy to remove the sear.<br />
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<br />
Once you have, remove the trigger assembly. To do this, press the trigger up from the bottom, and compress the disconnector spring enough that the trigger and disconnector come free from the sear assembly.<br />
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<br />
Now you have the trigger assembly in your hands. To install your brand new trigger, simply tap out the disconnector pin holding the trigger and disconnector together, and remove the disconnector and disconnector spring.<br />
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Replace trigger, or work on the trigger, or make sweet love to it, or whatever you're going to do, and then prepare to go insane.<br />
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<br />
This next step is the only truly hard part in replacing the trigger on a Vz. 58. You must reassemble the trigger group, which means reinserting the disconnector spring, and then compressing the disconnector to just the right place that the holes line up, while holding the trigger assembly steady, and hammering the disconnector pin back into the assembly. You might be able to more easily do that with a pin vise, but I don't have one of those, so I enlisted my girlfriend to supply the requisite third hand, but found that the assembly is actually too small for three hands to fit on the blasted thing without me hammering our thumbs into pulp.<br />
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Instead, I found a pair of pliers, and that worked well enough. It's still a matter of trial and error, though, so be patient, and eventually the pin will work its way a little into the disconnector, and then it's just a simple task of tapping the little devil in gently.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiubvU_lOs_XpLrW2iwqTpXQ1QC8Bmmp3u3USeXAapXPzwuJhu3c8o0tkJAZlmwGB5ul5Auzr20Drq3qmB421XtYvvopkGT9th7MnPtlSQcHWS-xksAxmnNaiIoyOMOJefD4i-sxYxYR7-2/s1600/P1080054.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiubvU_lOs_XpLrW2iwqTpXQ1QC8Bmmp3u3USeXAapXPzwuJhu3c8o0tkJAZlmwGB5ul5Auzr20Drq3qmB421XtYvvopkGT9th7MnPtlSQcHWS-xksAxmnNaiIoyOMOJefD4i-sxYxYR7-2/s320/P1080054.JPG" height="180" width="320" /></a></div>
<br />
Now that you have your trigger assembly back in one piece, you simply have to put it back in the way it came, and then pushing the pin back in. Do not put the e-clip back on the pin until you are 100% sure your trigger group works. I even went so far as to reassemble the entire rifle without the e-clips, just to make sure. Once the trigger is in there satisfactorily, start on the sear assembly.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdvRRSXeSb1da3CkksIoZCpAC4FaWasAFhdns76hBIFKVp0ar68E4rW8xoGm4W8U2HhyphenhyphenLVYMYEHZGcT8Ui-VZk3TM7DBvaCdsYiNw054qeDRhGRfezl6mKgh7SGqhkm4ilA_u3-2VI0A4g/s1600/P1080055.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdvRRSXeSb1da3CkksIoZCpAC4FaWasAFhdns76hBIFKVp0ar68E4rW8xoGm4W8U2HhyphenhyphenLVYMYEHZGcT8Ui-VZk3TM7DBvaCdsYiNw054qeDRhGRfezl6mKgh7SGqhkm4ilA_u3-2VI0A4g/s320/P1080055.JPG" height="180" width="320" /></a></div>
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It looks weird, but it's not difficult to do once you figure out what goes where. The sear assembly likes to come apart, especially that plastic thing, which I'm pretty sure is a replacement for an automatic mechanism, since it does basically nothing. Czechpoint doesn't sell this part, so if it breaks, you're SOL, I guess. Anyway, that do-nothing plastic thing fits with the large end toward the right, if your assembly came apart (mine did), and the sear fits with the long end basically sitting in the middle of the receiver, to hold the striker back before firing.<br />
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The sear group fits in so that the little tab jutting out from the bottom of the sear is pulled on by the disconnector. A little trial and error will make it fit properly. Interestingly, the sear and trigger pins are interchangeable, so don't worry that you got them mixed up.<br />
<br />
Once your rifle's trigger works, simply slide the e-clips back onto the pins. This is actually easier than it sounds, if you use a screwdriver. They might not click, exactly, but if they look like they're on, they are.<br />
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Now you're ready to reassemble the rifle. Simply tilt the muzzle of the rifle downward, let the bolt flop forward in the carrier, and mate the carrier and receiver together at the cutouts in the rifle rails. Slide the bolt forward. Now if the sear engages the striker, that's a good sign. If it doesn't, you have more work to do. Remove the carrier and find out where you screwed up. If it holds the striker, pull the trigger, both to make sure the trigger group will release it properly and to prepare the partially assembled rifle to receive the cover.<br />
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Now take the bigger, top spring in the receiver cover, and align it with the topmost hole in the bolt carrier. slide it in, making sure the lower striker spring falls into place inside the striker (they call it a "linear hammer", since the actual firing pin is a separate part). Now slide the cover in most of the way.<br />
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Make sure the little tabs jutting down from the inside edge of the cover mate with the receiver, or it won't go on right. Once it's properly inserted, push in the retaining pin, and you're all set.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0tag:blogger.com,1999:blog-5557913977913148366.post-90678733055818220992014-01-30T15:14:00.002-08:002014-05-30T22:22:48.298-07:00All 5.56 Replacements Suck<blockquote class="tr_bq">
<div style="text-align: center;">
<b><span style="font-size: x-small;">[The title of this blog post was mandated by the 196,800 Revolutions Per Minute Marketing Department]</span></b></div>
</blockquote>
<br />
One of the benefits of having a system that allows me to accurately create cartridges and predict their performance is that I am able to easily make comparisons and evaluate different configurations against each other in terms of weight, size, and performance. I previously used this method to create a standalone cartridge that satisfied Tony Williams' requirements for a GPC in <a href="http://196800revolutionsperminute.blogspot.com/2013/11/the-case-against-general-purpose.html">this post.</a> Today, I'm going to use it to create an example cartridge that shows in part why most larger-caliber 5.56 replacements offer virtually nothing over the cartridge they would replace.<br />
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First, we whip up a 5.56 load with the <a href="http://kwk.us/powley.html">Powley computer:</a><br />
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<a href="http://i.imgur.com/3wjniZ0.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/3wjniZ0.png" height="347" width="640" /></a></div>
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Naturally, I already had the 5.56 case rendered in Solidworks, based off <a href="http://i.imgur.com/gIdQCq6.jpg">the 5.56 case specification.</a> The figures for projectile length are those of the SS109 projectile, <a href="http://i.imgur.com/H6wvjJD.gif">a drawing of which can be found here.</a><br />
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Now, we'll whip up 5.56 necked up to 6.8mm. Let's use 6.8 SPC projectiles, so we'll need the same case length as 6.8 SPC (1.6864")...<br />
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<a href="http://i.imgur.com/0Bolzpk.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/0Bolzpk.png" /></a></div>
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We'll need to decide on a neck length for the new cartridge. 6.8 SPC has a relatively long neck, length, so I think we'll just use the neck length of 7.62x39. This'll make a fairly minor difference in performance, and I'm erring on the side of more, not less...<br />
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<a href="http://i.imgur.com/qpICS5Y.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/qpICS5Y.png" /></a></div>
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Here's our finished case:<br />
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<a href="http://i.imgur.com/IiFZpu5.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/IiFZpu5.png" /></a></div>
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Now, we have to find the case volume. To do this, we need to model the negative of the case interior, like this:<br />
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<a href="http://i.imgur.com/8rsfKo0.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/8rsfKo0.png" /></a></div>
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Then, once you have a solid model, we need to find the internal volume:<br />
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<a href="http://i.imgur.com/daKQMTX.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/daKQMTX.png" height="422" width="640" /></a></div>
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Alright, now we have the internal volume in grams H2O. Just divide by 1,000 and multiply by 15.43 to get the case capacity in grains H2O, which comes to 30.2 grs.<br />
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Now we need to find the length of the bullet we'll be using. Fortunately <a href="http://www.jbmballistics.com/ballistics/lengths/lengths.shtml">there's a handy list of these over at JBM Ballistics.</a> The Hornady 110gr V-Max is a 6.8 SPC bullet, and will be fine for this example. It has a length of 1.045. To the Powley computer:<br />
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<a href="http://i.imgur.com/ettTFFs.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/ettTFFs.png" height="348" width="640" /></a></div>
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Alright, now we have two sets of performance figures that are about as directly comparable as we're likely to get. Now we need to run them through a ballistic calculator, the best free one of which I am aware being the one at JBM Ballistics. This is, in my experience, a very accurate calculator, that compensates even for nonlinear increases in wave drag at supersonic speeds. So we enter the projectile weight, velocity, caliber, and set the maximum range to 500 meters, range increment to 100 meters, zero to 25 meters, and sight height to 1.5". We also check "ranges in meters", and in a dropdown menu select "Energy (Joules)". Next, we just need to find some accurate ballistic coefficient figures. Fortunately, <a href="http://196800revolutionsperminute.blogspot.com/2012/11/where-do-i-get-my-ballistic-coefficient.html">I have an Excel spreadsheet of such figures on my website,</a> which just so happens to include the value for the .277" Hornady 110gr V-Max. For 5.56, we'll derive a ballistic coefficient value with the same form factor as the V-Max, in the interests of keeping everything fair. We get a value of .159 G7, very close to SS109's .158.<br />
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Now we can get a good estimate of the performance of these two cartridges.<br />
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5.56:<br />
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<a href="http://i.imgur.com/jBGz3JC.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/jBGz3JC.png" height="640" width="467" /></a></div>
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...and our 6.8/5.56 cartridge with the 110gr V-Max:<br />
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<a href="http://i.imgur.com/1gjlJSF.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/1gjlJSF.png" height="640" width="474" /></a></div>
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Ahah! See? The 6.8mm provides a full 18% more energy at 500m than 5.56! I knew it! Larger calibers really <i>are</i> better!<br />
<br />
...Wait, is that the whole picture? After all, isn't the 6.8mm heavier? What good is a military round that produces somewhat more energy per shot if it doesn't end up saving you any weight? Well, to find out exactly how much heavier our 6.8mm is, we need to go back to Solidworks, and find out how heavy the cases of each round are:<br />
<br />
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<a href="http://i.imgur.com/ibTVZnA.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/ibTVZnA.png" height="374" width="640" /></a></div>
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<a href="http://i.imgur.com/NZfZc9i.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://i.imgur.com/NZfZc9i.png" height="374" width="640" /></a></div>
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We can see from this that the weight of the cases is very comparable. To get the actual weight of each case, we divide the highlighted figure by 1,000, and multiply by 8.4 (approximately the density of drawing brass). For 5.56, we get 6.372 g, and for our 6.8/5.56, we get 6.298 g. Next, we need to find the weight of the powder charge for each. Well, hey, we already know this, it's right there in the Powley computer results. Converting to grams by dividing by 15.43, we get 1.458 g for 5.56, and 1.283 g for our 6.8. Hey! So far the 6.8mm is winning!<br />
<br />
There are two more components left. One is the primer. I happen to know that small rifle primers weigh about .25 g, and both are cartridges use SRPs, so we'll add .25 g for both.<br />
<br />
The last component is the bullet. We know the bullet weights already; 62gr (4.02g) for 5.56 and 110gr (7.13g) for our 6.8. This is where the 6.8's minor lead in terms of weight gets completely shattered.<br />
<br />
Adding it all up, we get a total round weight of 12.1 g for the comparative 5.56 and 15.0 g for our 6.8mm cartridge.<br />
<br />
Now, if we take the energy at 500m and divide it by the weight of the cartridge, we can truly begin to compare these two cartridges. For 5.56, we get a value of 35.5 J/g@500m. For our 6.8mm, we get a value of... 33.7 J/g@500m. That's right, in terms of energy retained at range for every gram carried, the much-loathed 5.56mm actually comes out 5% <i>better</i> than its 6.8mm counterpart. Who'd have thought?<br />
<br />
Keep in mind that 5.56 also produces a vastly superior trajectory to the 6.8mm cartridge, having a whopping 81% less drop, 19% less wind drift, and 25% better time of flight, at 500m. Further, remember the principles of wounding when looking at these two cartridges. <a href="https://docs.google.com/viewer?url=http://www.dtic.mil/dtic/tr/fulltext/u2/705381.pdf">Smaller projectiles, all things being equal, tumble sooner than larger ones.</a> <a href="http://smg.photobucket.com/user/JC_Denton/media/4cb181ba.jpg.html">Faster projectiles tend to fragment more dramatically than slower ones.</a> Not only is the 6.8mm projectile much larger, it is also much slower. Therefore, we cannot expect it to exhibit fragmentation except at the absolute closest range, and even then, it will not do so very dramatically. If it tumbles, it will do so later than comparable 5.56 caliber projectiles, <a href="http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA240295">and may not deposit very much energy</a> (link begins a download) within a human target.<br />
<br />
Is this comparison perfect? No, it makes several compromises in exactness for the sake of clarity. Does it reflect every larger-caliber 5.56 challenger out there? No, but it does give the reader an idea of what effect increasing the caliber and projectile mass and reducing the velocity has on its performance and the overall weight of the cartridge (or, taken in the inverse, one might ask which produces better ballistics, 6.8 SPC or 6.8 SPC necked down to .22 caliber?). It is unfortunate that this material is too technical to be introductory, as it is so fundamental to understanding rifle cartridge design. Much time and effort that has been wasted might not have been if the designers of these medium-caliber intermediate cartridges had understood these principles.<br />
<br />
A closing note: This comparison humors the assumptions of many opponents of 5.56 that the amount of energy a cartridge produces per pound carried is the sum worth of that cartridge in combat. <a href="http://196800revolutionsperminute.blogspot.com/2014/01/the-new-caliber-mafia.html">I dispelled this notion of "stowed kills" in another post.</a> One should not confuse my demonstrating that 5.56 meets and beats many of these proposals on their own terms with my validating that method of evaluating cartridge performance for infantry rifles.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com9tag:blogger.com,1999:blog-5557913977913148366.post-46183158056018427992014-01-22T13:43:00.004-08:002016-01-07T16:35:01.131-08:00Incitatus (The Remarkable Reliability Of An AR-15)Much is said of the supposed unreliability of rifles in the AR-15 family. For those who know the rifle only from articles posted to the internet, it's obvious that the weapon is a massive failure. It's fragile, jams constantly, "shits where it eats", and chokes up completely when exposed to any sort of extreme environment.<br />
<br />
Well, that's what I believed once, anyway. The reality of the matter is that the AR-15 is a tremendously well designed, mature, and very reliable family of weapons. My first exposure to how very wrong I was about the AR-15 came when, frustrated by <a href="http://www.armalite.com/images/Manuals%5C180bman.pdf">substandard alternatives</a>, I broke down and bought the closest thing to a military M4 I could get - a Colt 6920, which I named <a href="http://en.wikipedia.org/wiki/Incitatus">"Incitatus"</a> as a jab at Colt's logo, its high price ($1400 at the time), and what I felt must surely be my own growing insanity.<br />
<br />
I shot the weapon and kept shooting it. From the beginning I fired <a href="http://www.barnaul.co.nz/ammunition/selection/rifle-2/5-56-x-45-223-rem">imported Russian steel cased ammunition</a> through it almost exclusively, almost begging it to choke, so that I would be proven right once and for all. I kept pushing it further, firing it in more and more testing conditions, in sub-zero temperatures, covered in dirt, through wind and rain and through some very nasty dust storms in New Mexico. I almost never cleaned it, and it usually saw at least a thousand rounds from the last time before I lubed it. It didn't matter. Nothing stopped it. In the span of about a year, I fired nearly 5,000 rounds of (mostly) steel-cased ammunition through the rifle, and <i>once</i> it failed to lock back on an empty magzine. I never had another malfunction of any kind.<br />
<br />
After all this, my old opinions of the rifle were thoroughly destroyed. So, this was the rifle the troops were using. It was a damned good one. <a href="http://196800revolutionsperminute.blogspot.com/2012/11/how-much-do-rifles-actually-weigh.html">It was almost freakishly light in comparison to its stablemates,</a> extremely reliable, and accurate enough for me to pluck the highest score three times in a row at Appleseed events.<br />
<br />
I stretched its legs, too. Far from the Internet wisdom that says the AR-15 is "only a 300 yard weapon", I consistently made hits with that same crappy Russian ammo out to 400, 600, and finally 900 yards before it began to struggle. What was all this I heard about the M4 being unsuitable for the fighting in Afghanistan? With the TA01NSN ACOG I'd bought a couple years earlier secondhand, Incitatus had very long legs, indeed.<br />
<br />
Later, upon hearing me gush a bit over my rifle, a classmate of mine who had served with the Army in Iraq and had a bad experience with the M16, challenged me to a bet: I would choose the worst of his bringback magazines, and try to fire a full 30 rounds through my Colt. If it didn't malfunction, he'd buy me a pack of beer. We chose a particularly nasty example that had bent feed lips, was more of a parallelogram than a box, and had broken all the welds along the spine and been re-welded - poorly. It was time for a range trip.<br />
<br />
Out to the wooded foothills of Colorado, we went. After a long dirt trail, barely traversed by my friend's '86 silver Toyota Camry, we stopped, and broke out our rifles and handguns, and began shooting. I gave my friends a background on the bet, and my girlfriend fired up my handheld Casio camera to record proof.<br />
<br />
<a href="https://www.youtube.com/watch?v=dcyuEOGOuUc&ab_channel=Tau">The rifle and magazine ran like a champ...</a> Through a total of about 150 rounds, in fact. By the end of the range day, I never got the magazine to cause the rifle to malfunction.<br />
<br />
I've read a lot of forum posts, blog posts, and magazine articles that bash the AR-15. For a while, I was convinced they all couldn't be wrong. I've since learned, not only how reliable an AR-15 can be even through neglect and tough conditions, but also not to jump to conclusions based only on an opinion I read somewhere.<br />
<br />
Having said that, I'll leave you with a few blog posts and online articles that buck this trend, and talk about the virtues of the AR-15:<br />
<br />
<a href="http://vuurwapenblog.com/2010/08/27/cleaning-your-ar-15-is-pretty-much-a-waste-of-time/">A blog post by Andrew Touhy on how cleaning your AR-15 is a waste of time.</a><br />
<br />
<a href="http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/">An article by Mike Pannone on the reliability of the AR-15 platform, the "shits where it eats" myth, and problems with maintenance in the service.</a><br />
<br />
<a href="http://weaponsman.com/?p=4158">Weaponsman weighs in on Congressional criticism of the M4.</a><br />
<br />
<a href="http://weaponsman.com/?p=2211">A report on early M16 reliability in Vietnam, from Weaponsman.</a><br />
<br />
<a href="http://weaponsman.com/?p=241">Weaponsman on why the SCAR-L was not adopted.</a><br />
<br />
<a href="http://weaponsman.com/?p=329">The forward assist on the M16/M4 is useless, says Weaponsman.</a><br />
<br />
<a href="http://weaponsman.com/?p=11181">M16 improvements from 1968, from Weaponsman.</a><br />
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<a href="http://weaponsman.com/?p=9200">M4 improvements, from Weaponsman.</a><br />
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<a href="http://weaponsman.com/?p=9194">US small arms reliability, from Weaponsman.</a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com1tag:blogger.com,1999:blog-5557913977913148366.post-66446615525397713782014-01-10T19:45:00.001-08:002015-03-06T21:28:54.175-08:00The New Caliber MafiaFirst there was the <a href="http://en.wikipedia.org/wiki/Bomber_Mafia">Bomber Mafia</a> in the 1930s, then there was the <a href="http://en.wikipedia.org/wiki/Fighter_Mafia">Fighter Mafia</a> in the 1970s. Now, in the oughts and teens of this century, we have a <a href="http://www.quarry.nildram.co.uk/The%20Next%20Generation.htm">Caliber Mafia.</a> How droll!<br />
<br />
On every corner of the military-related internet, it seems, one will be assailed by true believers who assure you that the 5.56mm and other small caliber high velocity cartridges are the products of a failed concept and must be replaced by something else, which inevitably must be much heavier and greater in caliber.<br />
<br />
<a href="http://196800revolutionsperminute.blogspot.com/2013/11/the-case-against-general-purpose.html">I've already addressed the technical concerns of why these calibers cannot replace 5.56 NATO and other SCHV cartridges in service.</a> This post will - unlike the last which addressed Mr. William's article specifically - be a more general response to the Caliber Mafia, incorporating a number of ideas mentioned in <a href="http://www.tank-net.com/forums/index.php?showtopic=38564">the Tanknet thread on that post.</a> Each section will address common arguments made by mafiosos, both those critical of 5.56mm and in favor of larger caliber cartridges.<br />
<br />
<b>I. Higher performance is attainable using modern powders</b><br />
<blockquote class="tr_bq">
<a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1050695">Ex. The 6.5mm Arisaka mentioned in TCA generated over 2,600 J from a 50mm-long case about the same diameter as the Grendel's over a century ago, without the benefit of modern powders, so the GPC should be usefully smaller as well as lighter (the Arisaka used a 9g spitzer bullet).</a></blockquote>
This argument is often used in concert with predictions of extravagant performance of a pet cartridge. For a start, propellant technology has been fairly stagnant for the past half a century. In addition, the energy density of the propellants has not improved much. Further, because the energy of the projectile is produced by the pressure curve of the propellant, gains basically cannot be made without slower burning propellants, and that only works up to a point, limited in military use by muzzle flash and muzzle thrust (the hypothetically ideal "plateau" burn curve can only be achieved by introducing more propellant into the combustion chamber after ignition has begun), as well as the practicality of loading large quantities of such ammunition quickly. As an example of how an improvement in velocity implies a rise in pressure, when nitrocellulose powders were introduced in the late 19th Century, the performance of cartridges of a given size greatly increased, but so too did the average peak pressure. Expecting significant gains in performance against historical cartridges without increasing peak pressure will thus leave one disappointed.<br />
<br />
The cited quote from Mr. Williams is a particularly good example of this, as he simply ignores several important factors in making this statement. For instance, the 6.5x50SR Arisaka produced between 2,500-2,600 J with an 800mm barrel, which is 60% longer than the barrel length prescribed for the GPC (20"/500mm). Thus, Mr. Williams makes a mistake in assuming that my statement at the end of <a href="http://196800revolutionsperminute.blogspot.com/2013/11/the-case-against-general-purpose.html">this post</a> was a predictive one; it was, rather, observational: It is highly unlikely that a cartridge will produce performance greatly superior to the 6.5 Arisaka from a significantly smaller cartridge if it is constrained to 20" barrels, even if it is using current propellants and pressure levels.<br />
<br />
<br />
<b>II. 5.56mm weapons are dead weight in long range engagements</b><br />
<blockquote class="tr_bq">
<a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1050695">Ex. The weight advantages of 5.56mm weapons and ammunition become irrelevant when a substantial proportion of small-arms engagements take place beyond their effective range - they then become useless dead weight.</a></blockquote>
<a href="http://weaponsman.com/?p=577">Riflemen are dead weight in long range engagements.</a> In fact, the last time this wasn't true, rifles came issued with volley sights and riflemen massed up in large formations, doing their best impression of a couple of mortar teams. The idea that a new caliber will change this seems a bit optimistic to me. There is a conversation worth having about the the increase in effective range of infantrymen from 300 to 500m brought about by the introduction of <a href="http://weaponsman.com/?p=2735">durable optical sights</a>. However, one should also consider that <a href="http://www.thegunzone.com/556dw-1.html">5.56 was originally intended to fulfill a 500m requirement,</a> which current-issue M855 ammunition improves upon considerably. A tentative conclusion that 5.56 is well-suited to 500m combat is thus reasonable.<br />
<br />
<br />
<b>III. Terminal ballistics is too complex for science</b><br />
<blockquote class="tr_bq">
<a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051201">Ex. You won't get scientific proof, because there are too many variables, as we all know: most importantly, the exact path of and damage inflicted by the bullet, plus the physical and mental state of the target. Laboratory tests cannot replicate these factors.</a></blockquote>
So help me god I've actually had to address this argument. Scientific inquiry is capable of producing far, far more complex deductions than those asked of a simple ballistics test. Laboratory experiments have been conducted that boggle the mind in their precision and control for numerous variables. To claim that a quantification of terminal effectiveness is "beyond science" is simply ludicrous. For posterity, I will re-post my suggestion for an experiment here:<br />
<blockquote class="tr_bq">
Shooting at live, restrained pigs connected to sphygmomanometers, heat rate monitors, ECG machines, and EEGs, counting only precise shots accurate to within a tolerance (determined by a medical professional) on a target area of the body (this could be the heart, brain, an artery, or lung, etc), a number of different rounds of ammunition, controlling for a variable (e.g., projectile weight or muzzle energy) are fired. The results from the devices are then measured and evaluated by medical professional of that specialty as well as veterinarians. Rinse and repeat for each variable you need to isolate.</blockquote>
<br />
<b>IV. Larger caliber cartridges are more effective, this expert doctor says so</b><br />
<blockquote class="tr_bq">
<a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051530">Ex. Dr. Grabinsky talks about rifle wounding mechanisms and effects. Incidence through torsos, especially longitudinally are usually very lethal. The reason being a longitudinal injury has more tissue for the bullet to begin yawing. If there is no yaw, then the major wounding effect (aside from striking bone) is going to be the wound cavity, permanent and temporary.</a><a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051530"><br /></a><a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051530">So, a larger bullet means larger wound cavity, temporary and permanent aka crush injury and stretch injury.</a></blockquote>
This follows from a misunderstanding of the term "wounding" as used in the medical sense, and a conflation of higher energy cartridges of 7.62mm caliber (such as .30-06) with lower energy cartridges of the same caliber (such as .30 Carbine) on the part of both doctors and the readers of their research. The difference between wounding as is relevant to the medical profession and incapacitation is explained in <a href="http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA240295">this document, from the Ballistics Research Laboratory.</a><br />
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A word about Dr. Martin Fackler: <a href="http://www.ajronline.org/doi/pdf/10.2214/ajr.155.4.2119095">His research</a> is often used to support arguments that only the permanent cavity of a wound channel matters for incapacitation, or that it matters the most. He himself does not say this anywhere, so far as I know. Fackler, instead, addresses (among other things) the notion that tissue around the wound in high velocity gunshot wounds <a href="http://farm9.static.flickr.com/8015/7231722056_9d0d0eab50.jpg">(which look quite nasty, indeed)</a> needs to be excised for treatment. His studies show that the tissue damaged by the temporary cavity will recover, and that energy deposition has no effect on <b>treatment,</b> saying nothing about incapacitation. Doctors, obviously, are concerned with the former, while small arms designers are largely concerned with the latter.<br />
<br />
<br />
<b>V. 5.56's terminal performance is unreliable; a larger caliber projectile will produce more consistent results</b><br />
<b><br /></b>
This is an argument I see implied almost any time the subject is brought up. Evidence of inconsistent terminal effectiveness in 5.56 is provided, and thus "we need a new, larger caliber" to fix it.<br />
<br />
<a href="http://www.dtic.mil/dtic/tr/fulltext/u2/705381.pdf">Evidence suggests that this will only make the problem worse.</a> If one is limited to Hague-compliant projectiles, then tumbling and fragmentation will be your primary vectors for terminal effectiveness. Not only do larger calibers (all things being equal) tumble less readily than smaller ones, they also often don't have enough velocity to fragment consistently. 6.8 SPC FMJBT bullets, for instance, hardly fragment at all, even at very close range. <a href="http://upload.wikimedia.org/wikipedia/commons/e/e9/RussianWP.jpg">Dr. Fackler even noted that 5.45x39 7N6 projectiles tended to upset sooner than 7.62x39 projectiles of similar construction.</a> The implied notion that, despite this, an additional few hundredths of a square inch frontal area will drastically improve effectiveness leaves me a bit skeptical.<br />
<br />
<br />
<b>VI. M855 fired from an M4 fragments out to only 50m</b><br />
<blockquote class="tr_bq">
<a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051809">Ex. After 200 m M855 doesn't fragment if fired from 20 in barrel (M16). From M4, it doesn't fragment at distances greater than some 50 m due to a lower mv that drops to the critical velocity at shorter distance. Shorter barrels are even worse.</a></blockquote>
The response to this is very nuanced and complex, and thus wholly unsuitable for the type of soundbyte-based debate that occurs on internet forums. While the fragmentation of small arms projectiles does change with the velocity at which they impact, use of the term "fragmentation threshold" can be misleading. If a projectile is fired at just below the fragmentation threshold, it performs much the same as if it is fired just above. The fragmentation threshold thus does not denote a drastic transition in performance of conventional jacketed small arms projectiles at a certain impact velocity. It is useful only in eyeballing how the projectile performs at different speeds, as at speeds below the threshold, no fragmentation occurs, while at speeds above it, fragmentation occurs in progressively more severe fashions. Only at very high velocities (typically over 2,900 ft/s, depending on jacket construction) does the familiar "confetti" fragmentation pattern occur. The reader should also keep in mind that fragmentation depends on many factors, the most important of which, besides impact velocity, is the construction of the bullet. Some materials fragment at very low velocities, while others may fragment only at velocities above that which is practical for nitrocellulose propellants. The figures used here are a "rule of thumb" for jacketed, lead-cored bullets, but even within that scope they can differ significantly from reality.<br />
<br />
I am going to try to make this as brief as I can, but this section of my response is fairly technical and involved, as it covers a "worst case" scenario for velocity at range for the M4 Carbine in some detail. A military barrel is considered to be worn out if it experiences a velocity loss of 200 ft/s or more vs. a new barrel. The standard set in <a href="http://www.everyspec.com/MIL-SPECS/MIL-SPECS-MIL-C/MIL-C-63989C_37913/">MIL-C-63989C</a> defines the average velocity of M855 from the M16A2 to be 3,000 ft/s (+/-40) at 78 feet from the rifle, which equals an average muzzle velocity of 3,081 ft/s. From the 14.5" barrel of the M4 Carbine, we can expect no more than a <a href="http://sadefensejournal.com/wp/?p=1093">9.6% reduction in velocity,</a>* for an average muzzle velocity of 2,811 ft/s. That gives us a muzzle velocity from our unserviceable barrel of 2,611 ft/s.<br />
<br />
Now, we can plug this figure into a ballistic calculator and see if our commenter is right. I am using the above velocity (2,611 ft/s), <a href="http://196800revolutionsperminute.blogspot.com/2012/11/where-do-i-get-my-ballistic-coefficient.html">a ballistic coefficient for M855 of .151,</a> a zero range of 25m, a maximum range of 500m, a range increment of 1m, and <a href="http://smg.photobucket.com/user/JC_Denton/media/4cb181ba.jpg.html">a minimum fragmentation velocity of 2,140 ft/s.</a>** The result is that the bullet reaches minimum fragmentation velocity at 154 meters. If a threshold of 2,300 ft/s is used (which I've seen quoted a few times), then it reaches that velocity at 101 meters. Only if a threshold of 2,500 ft/s is used does the fragmentation range drop below 50 m. This is not the minimum threshold of fragmentation, but the upper bound minimum velocity at which the jacket may split along the cannelure.<br />
<br />
Keep in mind, an M4 that clocks velocities this low is considered <b>unserviceable</b> and should be removed from service and fitted for a new barrel. If a more reasonable velocity of 2,970 ft/s* is used, the M4 Carbine stays above the 2,140 ft/s until 260 m, and above 2,300 ft/s until 207 m. Even if a threshold of 2,500 ft/s is used, a muzzle velocity of 2,970 ft/s gives a fragmentation range for the M4 of 143 m.<br />
<br />
*I don't think SADEF's figures are representative enough to be used outside of the scope of their experiment. The test was interesting, but I don't really think 9.6% velocity reduction is an accurate figure for the velocity loss going from 20" to 14.5" barrels (it results in approximately 50 ft/s lost per inch!). However, I'm using it here as a "worst case" example. <a href="http://armypubs.army.mil/doctrine/DR_pubs/dr_a/pdf/fm3_22x9.pdf">Field Manual 3-22.9</a> provides a more reasonable muzzle velocity figure for the M4 of 2,970 ft/s, which is a loss of about 25 ft/s per inch from the M16's nominal muzzle velocity of 3,100 ft/s.<br />
<br />
**I use a minimum fragmentation velocity of 2,140 ft/s, which is close to the lowest velocity at which fragments will come off of the bullet (usually shed from the lead core). The picture used as an example of this is of M193, but M855 performs basically the same way at comparable velocities, having the same jacket thickness.<br />
<br />
<b>Note:</b> There are a lot of different figures thrown around for the muzzle velocity of the M4, both in this section of this post and elsewhere on the Internet. While it may be desirable to keep a nominal muzzle velocity figure for a given rifle and ammunition on hand, one must remember that many factors affect the muzzle velocity of a rifle, beyond the type of ammunition fired and the barrel length of the gun. Such factors include - but are not limited to - the temperature of the ammunition just before firing, the profile and contour of the bullet, the shape and dimensions of the rifling, and the wear on the barrel. I took considerable effort to use the lowest velocity figures that seemed reasonable to me in every instance, to try to weigh the examination in favor of the idea that the M4 has a critically short fragmentation range. For example, FM 3-22.9 gives the muzzle velocity of the M16A2 as being 3,100 ft/s, not 3,081 ft/s (calculated from the specification in MIL-C-63989C). Even so, I was only able to achieve a fragmentation range of 50m by using a very high fragmentation "threshold" of 2,500 ft/s.<br />
<br />
<br />
<b>VII. 5.56 relies on fragmentation to incapacitate</b><br />
<br />
M855 and M193, like all military rifle projectiles, <a href="http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA240295">rely on energy deposition to incapacitate targets.</a> This is why ballistic gelatin is such a good indicator of performance, especially if high speed video footage is taken of the shot. At high velocities, 5.56mm FMJs will fragment, which can cause very grievous wounds indeed, but even if they do not fragment they will still tumble and deposit energy. Further, the single biggest factor in incapacitation is shot placement. It is unlikely that any 5.56mm projectile will incapacitate the target with a shot to an extremity, but <a href="http://vuurwapenblog.com/2010/05/25/657/">the same is also true of full-caliber 7.62mm projectiles, as well.</a> As noted before, <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/705381.pdf">smaller-caliber projectiles will tumble earlier than larger ones, all things being equal,</a> and thus will tend to deposit a greater percentage of their energy into the target.<br />
<br />
<br />
<b>VIII. 5.56 produces only 2,700 ft/s from the M4</b><br />
<br />
This is based on <a href="http://sadefensejournal.com/wp/?p=1093">a SADEF Journal article</a> using a nonstandard barrel, with ammunition chilled before firing for temperature consistency. It is not applicable to M4s with good condition barrels used in temperate conditions, which typically have muzzle velocities about 200 ft/s higher or more.<br />
<br />
<br />
<b>IX. Permanent cavity is the most important factor in incapacitation</b><br />
<br />
<a href="http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA240295">This Ballistics Research Laboratory paper</a> disagrees.<br />
<br />
<br />
<b>X. "Stowed kills"</b><br />
<blockquote class="tr_bq">
<a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1052127">Ex. If it takes 3 hits to put down a Taliban Fighter, are you saving weight over a cartridge that takes one hit to do so? I think not</a>.</blockquote>
This is the way I have seen the term "stowed kills" used in small arms circles (it is used in a completely different way when talking about AFVs): the speaker describes (explicitly or implicitly) some sort of modifying coefficient to ammunition. e.g., it has been argued that 6.8 SPC is 3.5 times effective as 5.56, and weighs 40% more, therefore it is overall 2.5 times as efficient as 5.56.<br />
<br />
I argue that this is nonsense. The reason being that very few rounds fired from infantry rifles ever hit their intended targets. Most infantrymen who've seen combat have not shot directly at another person very many times at all. I would hazard a guess that the number of enemies hit by ammunition fired from rifles in combat per combat veteran rifleman is decidedly in the single digits, and may even be less than one (I'm being extremely generous here, given figures from past wars). The number of rounds expended per combat veteran rifleman, however is assuredly much higher, probably in the triple digits bare minimum.<br />
<br />
Let's go with some ballpark figures. Say the average combat veteran rifleman expends 5,000 rounds of ammunition over his combined tours of duty, and hits and at least wounds 2 enemies in that time. That means, if he was using a 5.56mm rifle, he would have expended 60 kilograms worth of ammunition, only a few tens of grams of which had any physical affect on the target at all. Nearly 5,000 rounds he expended, minus the ones fired that hit their targets, produced exactly zero kills. Only a handful of cartridges were directly responsible for taking the enemy out of action, so even if a more poorly-performing caliber is used which requires a soldier to fire many more rounds to incapacitate a target, that fraction of the total rounds expended over that soldier's tours in terms of weight is still very small. This will be true regardless of whether the cartridge is 5.56mm, 7.62mm, or anything else. Therefore, "stowed kills" as it is typically used in the context of infantry rifles, is not a useful metric.<br />
<br />
<br />
<b>XI. Twist rate has no effect on the terminal effectiveness of 5.56mm</b><br />
<blockquote class="tr_bq">
<a href="http://www.ar15.com/ammo/project/term_tighttwist.html">Ex. Fact: Flesh is as much as 1000 times denser than air and will cause a bullet to lose stability almost instantly. For M193 and M855 ammo, this typically occurs after 3-5 inches of flesh penetration, though this can vary. In order to spin the bullet fast enough to be stable in flesh, the barrel twist would have to be on the order of 1 twist every 0.012 inches, which would look like the barrel had been threaded instead of rifled.</a></blockquote>
This unfortunately results from a misunderstanding of how a bullet travels in flight. It is true that a bullet spun by rifling cannot hope to remain stable for long in a mostly-water medium like tissue or ballistic gelatin. However, this is not the only factor in how and at what point in its travel the bullet will tumble.<br />
<br />
The twist rate of the barrel helps determines the stability of the projectile through media, in this case air. A tighter twist rate will better stabilize the projectile, reducing the <a href="http://en.wikipedia.org/wiki/Precession">precession</a> of the bullet (the degree to which it deviates axially from the flight path). It is this reduced angular deviation that can cause through-and-through wounds, not the bullet being stable through flesh. In other words, <a href="https://docs.google.com/viewer?url=http://wstiac.alionscience.com/pdf/WQV8N1_ART01.pdf">a bullet stabilized by a 1-in-7 twist rate barrel may hit the target at a shallower angle and thus yaw later</a> than one stabilized by a 1-in-9 twist rate barrel. I highly suspect this is why you will be hard pressed to find a gel test video online of M855 being fired from a 1-in-9 twist rate barrel and failing to upset within about the first 5".<br />
<br />
Somewhat paradoxically, this tight twist rate should give M855 exceptionally consistent long-range terminal effectiveness. The same excellent stabilization that minimized precession also ties the bullet more closely to its original orientation through its flight. That means that at long range the bullet is flying through the air at an upward angle relative to the arc of its flight. If it hits a target at this angle, it should upset readily and tumble within the first few inches of tissue.<br />
<br />
<b>EDIT (3/23/2014):</b> It seems I may be wrong about this. A closer reading of <i><a href="http://www.dtic.mil/dtic/tr/fulltext/u2/a519801.pdf">Small Caliber Lethality</a></i> shows that in testing longer projectiles which would have been less well stabilized than M855 from 1/7 twist barrels, they found virtually no difference in fleet yaw from M855 and any other caliber tested, including M80. The reason for this erratic performance is that within 50m the projectiles have not yet settled into stable precession caused by their rifling (something I am wholly unqualified to describe). More on this <a href="http://www.dtic.mil/ndia/2005smallarms/tuesday/newill.pdf">can be found here.</a> While the AR-15.com explanation of twist rate's effect on lethality is still incomplete, it seems my theory wasn't quite on the mark, either. I am leaving the incorrect explanation up as a record of my mistake.<br />
<br />
<br />
<b>XII. The GPC concept was formulated in light of experiences in Afghanistan</b><br />
<br />
<a href="http://www.tank-net.com/forums/index.php?showtopic=36483&p=959879">Mr. Williams will freely admit</a> <a href="http://www.quarry.nildram.co.uk/6.5mm%20GPC.jpg">he first came up with the concept in the early '70s</a>, which inclines me to believe that he has come up with requirements to suit his concept, and not the other way around. Regardless of the merit (or lack thereof) of the GPC idea, it is clear that it was <b>not</b> developed in light of recent experiences overseas.<br />
<br />
<br />
<b>XIII. Soldiers are unhappy with the performance of 5.56</b><br />
<br />
Soldiers may be unhappy with many things, but there's no reason to believe the performance of 5.56 has not been satisfactory. <a href="http://www.thebangswitch.com/the-poodle-killer-myth/">Several</a> <a href="http://vuurwapenblog.com/2010/06/23/info-on-5-56mm-effectiveness-from-sweden/">notable</a> <a href="http://vuurwapenblog.com/2010/05/25/657/">combat</a> <a href="http://weaponsman.com/?p=5798">veterans</a> have commented on their satisfaction with the cartridge, noting especially its light weight. <a href="http://www.youtube.com/watch?v=BDoX8UnQ4D0">Video evidence</a> corroborates its effectiveness in skilled hands, even at long range.* Given this, it is somewhat strange to be met with constant cries of "the soldiers don't want it!" which cannot then be corroborated with actual sources, anecdotal or otherwise. Often <a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051201">"after action reports"</a> that support the idea that 5.56 is inadequate are implied to exist, but when asked to produce these reports, <a href="http://www.tank-net.com/forums/index.php?showtopic=38564&p=1051546">the speaker cannot supply anything of the sort.</a><br />
<br />
*The ammunition used here is the 77gr Mk. 262 special purpose ammunition, not M855. At 800m, neither projectile fragments, but both tumble readily.<br />
<br />
<br />
<b>EDIT (3/6/2014) XIV: 5.56mm produces inadequate suppression effect for an infantry rifle cartridge</b><br />
<br />
Mr. Williams has become quick to claim that 5.56mm produces inadequate suppressive effect - by way of a small sonic boom - and that a 6.5mm weapon would do much better.<br />
<br />
What this ignores is how sonic booms are actually generated, and what aspects of a radially symmetrical body enhance or mute the boom. Fundamentally, the boom is created by the pressure wave, and is closely related to how drag operates on the body itself - which is more a function of shape than size. I'm don't have an Aero/Astro degree, so I can't really go into detail here, but it's important to note that while larger bodies do create larger sonic booms, a .264" bullet from a GPC is simply not bigger enough than a .224" bullet from a 5.56mm round to make an appreciably larger sonic boom. Further, a center piece of the GPC concept is the use of elongated, low drag bullets. These bullets, for exactly the same reason that they retain energy well, <a href="http://en.wikipedia.org/wiki/Shaped_Sonic_Boom_Demonstration">will produce inferior sonic booms</a> to those that have inferior ballistic shape. The energy for the sonic boom can only come from one place: The projectile itself as it moves through the air. Therefore, lower drag bullets will <i>necessarily</i> produce smaller, less audible sonic booms than higher drag ones; they simply do not expend as much energy in flight.<br />
<br />
One way that the GPC could potentially produce louder sonic booms is that it retains <i>velocity</i> better, which is a major component in sonic boom generation. However, the GPC only exceeds the velocity of 5.56mm (when fired from comparable barrel lengths) at 250m, and 5.56mm only becomes subsonic at 700m, meaning the gains in this area may well be negligible.<br />
<br />
Overall, the biggest problem with Mr. Williams' theory about the sonic boom-producing ability of the GPC is that he has provided no direct evidence for it. Further, the overwhelmingly most important factor in the suppression of enemies is how close the bullets impact to the target. The round that an infantryman will miss less badly with is the round he can carry and shoot without tiring for the longest, given an adequately flat trajectory.<br />
<br />
<br />
<b>In Sum:</b><br />
<br />
There is not sufficient weight to the arguments of the Caliber Mafia to compel me to take their ideas seriously, much less for any military to actually implement any of their proposed calibers as standard issue. While the 5.56mm caliber and the two-caliber system may not be ideal, it is sufficient to meet current needs, so far as this author can tell. What does the future hold? Who knows? Whatever the next infantry rifle cartridge is, however, <a href="http://196800revolutionsperminute.blogspot.com/2013/10/small-caliber-high-velocity-isnt-new.html">it is unlikely to produce significantly less velocity or fire projectiles any larger in caliber than 5.56mm.</a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com6tag:blogger.com,1999:blog-5557913977913148366.post-18300281283641667342013-11-20T23:48:00.001-08:002017-09-06T12:12:24.016-07:00Steel-Cored Armor Piercing Loads for 5.56mmAs body armor improves and as the presence of lightly armored vehicles increases on the battlefield, it is reasonable to expect that inexpensive steel cored armor piercing rounds will become more desirable. Currently, there are 5 steel cored armor piercing loads widely available, in all calibers: .30-06 <b>M2</b>, 7.62x51 <b>M61</b>, 7.62x54R <b>BP</b>, 5.45x39 <b>7N22</b>, and 5.8x42 <b>DBP-10</b>.<br />
<br />
These loads provide a good starting point for designing a new steel-cored AP round for the 5.56mm.To gain some idea of the effectiveness of each projectile's core, we will examine their respective length-to-diameter ratios, gleaned from images of the sectioned bullets. Unfortunately, I was unable to find any reference material for the Russian 7.62mm BP projectile. The rest are as follows:<br />
<br />
<blockquote class="tr_bq">
M2: Between 4.1 and 4.6 calibers, depending on sample </blockquote>
<blockquote class="tr_bq">
M61: Between 3.3 and 3.7 calibers, depending on sample </blockquote>
<blockquote class="tr_bq">
7N22: 5.2 calibers</blockquote>
<blockquote class="tr_bq">
DBP-10: 4.9 calibers</blockquote>
<br />
Because the M2 and M61 cores have such uncompetitive L/D ratios, we will forgo scaling those projectiles down, and instead focus on analogues to the 7N22 and DBP-10.<br />
<br />
Scaling the 7N22 projectile to .224" caliber, we get a weight of 59.9 grs and a length of 1.020". Doing the same for the DBP-10, we get a weight of 60.7 grs and a length of 1.015. So far, both bullets seem very comparable, with the 7N22 projectile having a somewhat higher ballistic coefficient.<br />
<br />
Bullet seating will be calculated both for the intended depth of the original 7N22 ammunition, and to fit within 5.56mm's OAL, respectively. The former produces a figure of 2.488" overall length.<br />
<br />
The 5.8mm caliber has two versions: one intended for rifles, and one intended for DMRs and machine guns. The former has an overall length of 58mm, while the latter has an overall length of 61mm. The case length is 42mm, giving the each bullet 16mm and 19mm of exposure, respectively. We will use these figures, adjusted for caliber to 15.19mm (.598") and 18.03mm (.710"), as well as the original figure for 5.56mm of 12.70mm (.500") to give us overall lengths for each.<br />
<br />
Utilizing the Powley Computer, we can determine performance for all five configurations:<br />
<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicyuK5tsDAEErkDR7_Oe76WNMQ_TnBw3NwI5389W3rPUNXPa_Ccrp23fcUNr3837dppEUiCNnKRsr9nvBp1pUGBAJ992L-jAzWAh4Wvp5uMATtFbShQDYb9YFgbcALW_zIWUEFIplh1eAT/s1600/5567n22bulletandoal_zps2038a85c.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="712" data-original-width="811" height="561" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicyuK5tsDAEErkDR7_Oe76WNMQ_TnBw3NwI5389W3rPUNXPa_Ccrp23fcUNr3837dppEUiCNnKRsr9nvBp1pUGBAJ992L-jAzWAh4Wvp5uMATtFbShQDYb9YFgbcALW_zIWUEFIplh1eAT/s640/5567n22bulletandoal_zps2038a85c.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 1: 5.56mm with scaled up 7N22 bullet and the same relative seating depth as 5.45mm</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigaPHwf16gKaYLV2nvPlsUy34nhAqxaeO3VnhowcUtR_tiX3oULltOhVZdtZs9ob1lggQpH6f5__-TgbPK9kr8NQJo5AZCPbpx3CRmDoLc3Hl_0sonoATtIeST1Y2MPUlo4g4LwLE-qwrT/s1600/5567n22bullet_zpsdc666bae.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="712" data-original-width="811" height="560" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigaPHwf16gKaYLV2nvPlsUy34nhAqxaeO3VnhowcUtR_tiX3oULltOhVZdtZs9ob1lggQpH6f5__-TgbPK9kr8NQJo5AZCPbpx3CRmDoLc3Hl_0sonoATtIeST1Y2MPUlo4g4LwLE-qwrT/s640/5567n22bullet_zpsdc666bae.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 2: 5.56mm with scaled up 7N22 bullet</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjS7sQ8ejwu5XFB12US_0hvSlzjj_XmH842N324SxnVdjsN0BbwamyRsNYIz9MABPb7XVdZndfB_2MOG_yBLRv6ZErT0n0T4DImqlSuin6rGOkx18dDUUoAx11LmTL-PwAd2pNG7cieCIcp/s1600/556dbp10bulletandsniperoal_zps728613ff.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="712" data-original-width="811" height="560" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjS7sQ8ejwu5XFB12US_0hvSlzjj_XmH842N324SxnVdjsN0BbwamyRsNYIz9MABPb7XVdZndfB_2MOG_yBLRv6ZErT0n0T4DImqlSuin6rGOkx18dDUUoAx11LmTL-PwAd2pNG7cieCIcp/s640/556dbp10bulletandsniperoal_zps728613ff.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 3: 5.56mm with scaled down DBP-10 bullet and the same relative seating depth as 5.8mm heavy ball</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiOlPz82zo2gJ6TKN4hkjBznFiiYZkXvjnxE63-4yLOz2-K6O6iY4CQzbW5h7VZxvjWVAz9f3XUIbf4IE6smjFpF2q3aHUlJce2pJ4sKgdOdjKhD-nfi4Fewvjhnj2Fq2QV4kYfsP-VFPZ/s1600/556dbp10bulletandrifleoal_zps3bf23e95.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="712" data-original-width="811" height="560" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiOlPz82zo2gJ6TKN4hkjBznFiiYZkXvjnxE63-4yLOz2-K6O6iY4CQzbW5h7VZxvjWVAz9f3XUIbf4IE6smjFpF2q3aHUlJce2pJ4sKgdOdjKhD-nfi4Fewvjhnj2Fq2QV4kYfsP-VFPZ/s640/556dbp10bulletandrifleoal_zps3bf23e95.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 4: 5.56mm with scaled down DBP-10 bullet and the same relative seating depth as 5.8mm light ball</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8N74yvNtUQnRmHPxnB3s8MlNKcyzQxlbSYasbpdyHTFEVjgL1EjSoGF7YUuQgyFBiOzE_RFVJM8jSDRDFKbU-tAPazrlwgeetQZ1T4MOSESYM714ARA-FcFjLJ07A1HgJWrJqM_EBZxQu/s1600/556dbp10bullet_zpsc4e7427d.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="712" data-original-width="811" height="560" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8N74yvNtUQnRmHPxnB3s8MlNKcyzQxlbSYasbpdyHTFEVjgL1EjSoGF7YUuQgyFBiOzE_RFVJM8jSDRDFKbU-tAPazrlwgeetQZ1T4MOSESYM714ARA-FcFjLJ07A1HgJWrJqM_EBZxQu/s640/556dbp10bullet_zpsc4e7427d.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 5: 5.56mm with scaled down DBP-10 bullet</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZELqM4ztI3IsjhvrUwltXKKdECZ7sthHZ3Q0aH_4HKT957gx-CiHsN1j3Wm5REwNcfLmewTeUYVcZQQxurOFgZv-EwJZhTJfoPj5m3SK9Q3jCUhSQLj37BUbqejqesc-Sco7IaenriurQ/s1600/5567n22bullet_zpsdc666bae.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="712" data-original-width="811" height="560" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZELqM4ztI3IsjhvrUwltXKKdECZ7sthHZ3Q0aH_4HKT957gx-CiHsN1j3Wm5REwNcfLmewTeUYVcZQQxurOFgZv-EwJZhTJfoPj5m3SK9Q3jCUhSQLj37BUbqejqesc-Sco7IaenriurQ/s640/5567n22bullet_zpsdc666bae.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 5: 5.56mm with scaled down DBP-10 bullet</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgItda03WLXWCquAkdkCVEOkG4Ar4voOe33-99s6FjBw0QRfzvjzblwdyu96KRaNPvnDjqfn5DxFzKYd-TINcD6J0HBhKlsxWcpqLGxk1GlR3l0ZIVs34u4AfnMSpKUNHjyUpfwt6qKU3mN/s1600/556HVAP60grDisplay_zps772f5e0f.png" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" data-original-height="410" data-original-width="221" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgItda03WLXWCquAkdkCVEOkG4Ar4voOe33-99s6FjBw0QRfzvjzblwdyu96KRaNPvnDjqfn5DxFzKYd-TINcD6J0HBhKlsxWcpqLGxk1GlR3l0ZIVs34u4AfnMSpKUNHjyUpfwt6qKU3mN/s1600/556HVAP60grDisplay_zps772f5e0f.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 6: A hypothetical 55gr steel-cored 5.56mm AP load</td></tr>
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As we can see, performance is very similar for all types. The ideal configuration might be found in an adapted DBP-10 projectile - perhaps with a proportionally larger core - designed to fit within the existing 2.26" OAL of 5.56mm. This would give comparable performance to the DBP-10 within 500m, and cause minimal logistical disruption. The projectile could have reverse-drawn jacket with closed tip giving it a good ballistic coefficient and excellent accuracy, while conforming to international treaties. The finished product might look something like the render in figure 6.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com4tag:blogger.com,1999:blog-5557913977913148366.post-75709772296135945392013-11-10T14:51:00.003-08:002015-03-22T13:08:54.821-07:00The Case Against a General-Purpose Cartridge<blockquote class="tr_bq">
<b>Despite my efforts to keep to one system, this article hops between metric and imperial units quite a bit. Often, alternate units will be contained within parenthesis following a figure, but it's always a good idea to keep conversion factors handy when working with small arms. I use 25.4 millimeters to the inch, 3.28 feet per meter, 145 PSI per MPA, and 15.43 grains per gram.</b></blockquote>
<br />
Anthony Williams - an internet military enthusiast, collector, and author - is the primary online proponent of the universal rifle/machine gun caliber. <a href="http://www.quarry.nildram.co.uk/The%20Next%20Generation.htm">The General-Purpose Cartridge,</a> as he calls it, would theoretically combine the lethality and range of a 7.62mm weapon with weapons and ammunition closer to 5.56mm systems in weight. While he never lays out the requirements for such a round in an organized fashion, a clear picture can be formed from select lines in his article:<br />
<br />
<blockquote class="tr_bq">
<i>This indicates that the muzzle energy, weight and calculated recoil of the GPC should be approximately midway between the 5.56 and 7.62 - similar to the 6.8 Remington and 6.5 Grendel.</i></blockquote>
<blockquote class="tr_bq">
<i>The bullet's performance at 1,000 metres should be comparable with the 7.62 M80 ball, as measured by hit probability (a function of trajectory, flight time and susceptibility to wind drift) and damage potential (bullet energy and penetration).</i></blockquote>
<br />
Is the GPC as envisioned by Mr. Williams and his fellows possible? Is it desirable? Is it cost-effective? Previously, I have been very taken the idea of a unified rifle and machine gun cartridge for the military. As a result, I am highly familiar with the multitude of variations on this same concept: ranging from <a href="http://www.65grendel.com/forum/showthread.php?6543-Lets-start-over-how-do-you-design-a-GPC&s=072ca9f1ba4b651c0382469dd0c15c03&p=65550&viewfull=1#post65550">.276 Pedersen copycats,</a> to <a href="http://demigodllc.com/articles/6.8-mm-spc-cartridge-history-development-hornady-stag-arms-carbine/">kurz cartridge revivals,</a> to <a href="http://www.g2mil.com/6mm_optimum_cartridge.htm">miniaturized big game hunting magnums,</a> to Mr. Williams' ambitious 6.5/8/800. While the focus of this article is primarily to address the GPC, I will argue that, relative to the 5.56mm and 7.62mm cartridges now in service, all of these proposals fail to satisfy at least one of the three criteria. Some are technically feasible and perform better than either 7.62 or 5.56, but not enough better to warrant the expense and logistical disruption needed to field them. Some are technically feasible, but offer no advantage over the existing calibers while being saddled with significant downsides. Finally, some, such as Mr. Williams' 6.5/8/800, are simply technically unfeasible as currently imagined.<br />
<br />
<br />
The first group of cartridges all greatly resemble (though none improve upon) the .276 Pedersen. These include the <a href="http://7x46mmuiac.com/7x46mm_Cartridge.html">7x46mm UIAC,</a> the .270 Sidewinder, the .280 British, and others. The second-most mature group, many have examples have actually been loaded and fired, and the .280 British was even officially adopted, briefly. Because their performance has been verified, it cannot be said that these cartridges are unfeasible, but is it worth the cost and effort to field one, in light of the widespread adoption of 7.62mm weapons? In a word, no. Even <a href="http://www.thefirearmblog.com/blog/2010/04/07/7x46mm-uiac-universal-intermediate-assault-cartridge/">the literature for 7x46mm UIAC</a> shows it's not greatly more efficient than 7.62 NATO, and it doesn't provide any additional capability, so why would military procurement spend millions re-arming with entirely new weapons and ammunition when they have almost-as-good-and-already-in-the-inventory 7.62 NATO machine guns and rifles? <a href="http://196800revolutionsperminute.blogspot.com/2012/11/how-much-does-your-ammo-weigh.html">Since these cartridges are also almost as heavy as 7.62,</a> they offer little practical benefit and will be largely passed over.<br />
<br />
<br />
Due to a growing sense of doubt about the effectiveness of 5.56, numerous cartridges that I would characterize as belonging to the second category have been proposed. These include the 6.8 SPC, the .300 Blackout, the 7.62x40 Wilson Tactical, and more obscure cartridges, like the 6mm-223, <a href="http://sskindustries.com/6-5-mpc">6.5x42 MPC,</a> <a href="http://www.angelfire.com/art/enchanter/bullet.html">6.8mm ARC,</a> and <a href="http://www.scribd.com/doc/31780418/Small-Arms-Ammunition-for-the-21st-Century-high-performance-Alternatives-to-the-5-56-Nato-Round-infantry-May-june-2006">6x41mm SCC.</a> These cartridges all share greater projectile mass and lower velocity than 5.56mm, and relatively small cases, so that existing 5.56mm rifles can be rechambered for them, if necessary.<br />
<br />
My analysis of this category will be short: They are a technological step backwards. Their low velocity (typically not above 800 m/s, with some even below 700 m/s) and non-exceptional projectiles (typically with low sectional densities comparable to 5.56mm) produce ballistics inferior to that of the M4 Carbine in terms of trajectory, while offering little to no more energy at range for every pound carried.<b> </b>Most of the literature on these cartridges stresses their superior energy at range per shot to 5.56mm. Usually, this is true, but these cartridges come saddled with so much extra weight compared to 5.56mm that the advantage, if there was any there in the first place, is moot. A short example is as follows:<br />
<br />
<blockquote class="tr_bq">
<table class="data_table" style="background-color: #f8f8f8; border-spacing: 5pt 1pt; font-family: sans-serif; font-size: 9pt; font-weight: 900;"><tbody>
<tr><td><center>
<table class="data_table" style="border-spacing: 5pt 1pt; font-size: 9pt; font-weight: 900; width: 100%px;"><tbody>
<tr class="page_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="page_title_col" colspan="4"><span style="color: #444444;">Trajectory</span></td></tr>
<tr class="section_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="section_title_col" colspan="4"><span style="color: #444444;">Input Data</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell"><span style="color: #444444;">Ballistic Coefficient:</span></td><td class="input_value_cell" style="text-align: right;"><span style="color: #444444;">0.151 G7</span></td><td class="input_desc_cell"><span style="color: #444444;">Caliber:</span></td><td class="input_value_cell" style="text-align: right;"><span style="color: #444444;">0.224 in</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell"><span style="color: #444444;">Bullet Weight:</span></td><td class="input_value_cell" style="text-align: right;"><span style="color: #444444;">62.0 gr</span></td><td class="input_desc_cell"></td><td class="input_value_cell" style="text-align: right;"></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Muzzle Velocity:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">2950.0 ft/s</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Distance to Chronograph:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">10.0 ft</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Sight Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1.50 in</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Sight Offset:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.00 in</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Zero Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.00 in</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Zero Offset:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.00 in</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Windage:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.000 MOA</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Elevation:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.000 MOA</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Line Of Sight Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.0 deg</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Cant Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.0 deg</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Wind Speed:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">10.0 mph</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Wind Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">90.0 deg</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Speed:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">10.0 mph</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">90.0 deg</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">12.0 in</span></td><td class="input_desc_cell" colspan="1"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Temperature:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">59.0 °F</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Pressure:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">29.92 in Hg</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Humidity:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0 %</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Altitude:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.0 ft</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Vital Zone Radius:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">5.0 in</span></td><td class="input_desc_cell" colspan="1"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Std. Atmosphere at Altitude:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Pressure is Corrected:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">Yes</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Zero at Max. Point Blank Range:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Relative Drops:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">Yes</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Mark Sound Barrier Crossing:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Include Extra Rows:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Column 1 Units:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1.00 in</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Column 2 Units:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1.00 MOA</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Round Output to Whole Numbers:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
<tr class="section_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="section_title_col" colspan="4"><span style="color: #444444;">Output Data</span></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Elevation:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">6.951 MOA</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Windage:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.000 MOA</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Atmospheric Density:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.07647 lb/ft³</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Speed of Sound:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1116.4 ft/s</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Maximum PBR:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">305 m</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Maximum PBR Zero:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">261 m</span></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Range of Maximum Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">147 m</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Energy at Maximum PBR:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">740.6 J</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Sectional Density:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.177 lb/in²</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
</tbody></table>
<table class="output_table" style="border-spacing: 5pt 1pt; font-size: 9pt; font-weight: 900; width: 100%px;"><tbody>
<tr class="section_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="section_title_col" colspan="11"><span style="color: #444444;">Calculated Table</span></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Range</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Drop</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Drop</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Windage</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Windage</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Velocity</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Mach</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Energy</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Time</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Lead</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Lead</span></th></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(m)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(in)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(MOA)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(in)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(MOA)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(ft/s)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(none)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(J)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(s)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(in)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(MOA)</span></th></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">0</span></td><td class="drop_length_cell"><span style="color: #444444;">-1.5</span></td><td class="drop_angle_cell"><span style="color: #444444;">***</span></td><td class="wind_length_cell"><span style="color: #444444;">0.0</span></td><td class="wind_angle_cell"><span style="color: #444444;">***</span></td><td class="velocity_cell"><span style="color: #444444;">2960.7</span></td><td class="mach_cell"><span style="color: #444444;">2.652</span></td><td class="energy_cell"><span style="color: #444444;">1635.9</span></td><td class="time_cell"><span style="color: #444444;">0.000</span></td><td class="lead_length_cell"><span style="color: #444444;">0.0</span></td><td class="lead_angle_cell"><span style="color: #444444;">***</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">100</span></td><td class="drop_length_cell"><span style="color: #444444;">3.9</span></td><td class="drop_angle_cell"><span style="color: #444444;">3.4</span></td><td class="wind_length_cell"><span style="color: #444444;">1.2</span></td><td class="wind_angle_cell"><span style="color: #444444;">1.1</span></td><td class="velocity_cell"><span style="color: #444444;">2619.9</span></td><td class="mach_cell"><span style="color: #444444;">2.347</span></td><td class="energy_cell"><span style="color: #444444;">1281.0</span></td><td class="time_cell"><span style="color: #444444;">0.118</span></td><td class="lead_length_cell"><span style="color: #444444;">20.7</span></td><td class="lead_angle_cell"><span style="color: #444444;">18.1</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">200</span></td><td class="drop_length_cell"><span style="color: #444444;">3.2</span></td><td class="drop_angle_cell"><span style="color: #444444;">1.4</span></td><td class="wind_length_cell"><span style="color: #444444;">5.2</span></td><td class="wind_angle_cell"><span style="color: #444444;">2.3</span></td><td class="velocity_cell"><span style="color: #444444;">2301.2</span></td><td class="mach_cell"><span style="color: #444444;">2.061</span></td><td class="energy_cell"><span style="color: #444444;">988.2</span></td><td class="time_cell"><span style="color: #444444;">0.251</span></td><td class="lead_length_cell"><span style="color: #444444;">44.3</span></td><td class="lead_angle_cell"><span style="color: #444444;">19.3</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">300</span></td><td class="drop_length_cell"><span style="color: #444444;">-5.4</span></td><td class="drop_angle_cell"><span style="color: #444444;">-1.6</span></td><td class="wind_length_cell"><span style="color: #444444;">12.6</span></td><td class="wind_angle_cell"><span style="color: #444444;">3.7</span></td><td class="velocity_cell"><span style="color: #444444;">2006.2</span></td><td class="mach_cell"><span style="color: #444444;">1.797</span></td><td class="energy_cell"><span style="color: #444444;">751.1</span></td><td class="time_cell"><span style="color: #444444;">0.404</span></td><td class="lead_length_cell"><span style="color: #444444;">71.1</span></td><td class="lead_angle_cell"><span style="color: #444444;">20.7</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">400</span></td><td class="drop_length_cell"><span style="color: #444444;">-24.5</span></td><td class="drop_angle_cell"><span style="color: #444444;">-5.3</span></td><td class="wind_length_cell"><span style="color: #444444;">24.1</span></td><td class="wind_angle_cell"><span style="color: #444444;">5.3</span></td><td class="velocity_cell"><span style="color: #444444;">1732.3</span></td><td class="mach_cell"><span style="color: #444444;">1.552</span></td><td class="energy_cell"><span style="color: #444444;">560.0</span></td><td class="time_cell"><span style="color: #444444;">0.580</span></td><td class="lead_length_cell"><span style="color: #444444;">102.1</span></td><td class="lead_angle_cell"><span style="color: #444444;">22.3</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">500</span></td><td class="drop_length_cell"><span style="color: #444444;">-57.5</span></td><td class="drop_angle_cell"><span style="color: #444444;">-10.0</span></td><td class="wind_length_cell"><span style="color: #444444;">40.7</span></td><td class="wind_angle_cell"><span style="color: #444444;">7.1</span></td><td class="velocity_cell"><span style="color: #444444;">1476.1</span></td><td class="mach_cell"><span style="color: #444444;">1.322</span></td><td class="energy_cell"><span style="color: #444444;">406.6</span></td><td class="time_cell"><span style="color: #444444;">0.785</span></td><td class="lead_length_cell"><span style="color: #444444;">138.2</span></td><td class="lead_angle_cell"><span style="color: #444444;">24.1</span></td></tr>
</tbody></table>
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<tr class="credit_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 8pt; text-align: right;"><td class="credit_cell"><span style="color: #444444;">10/11/13 18:34, <a href="http://www.jbmballistics.com/">JBM</a>/<a href="http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi">jbmtraj-5.1.cgi</a></span></td></tr>
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<table class="data_table" style="background-color: #f8f8f8; border-spacing: 5pt 1pt; font-family: sans-serif; font-size: 9pt; font-weight: 900;"><tbody>
<tr><td><center>
<table class="data_table" style="border-spacing: 5pt 1pt; font-size: 9pt; font-weight: 900; width: 100%px;"><tbody>
<tr class="page_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="page_title_col" colspan="4"><span style="color: #444444;">Trajectory</span></td></tr>
<tr class="section_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="section_title_col" colspan="4"><span style="color: #444444;">Input Data</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell"><span style="color: #444444;">Ballistic Coefficient:</span></td><td class="input_value_cell" style="text-align: right;"><span style="color: #444444;">0.180 G7</span></td><td class="input_desc_cell"><span style="color: #444444;">Caliber:</span></td><td class="input_value_cell" style="text-align: right;"><span style="color: #444444;">0.277 in</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell"><span style="color: #444444;">Bullet Weight:</span></td><td class="input_value_cell" style="text-align: right;"><span style="color: #444444;">110.0 gr</span></td><td class="input_desc_cell"></td><td class="input_value_cell" style="text-align: right;"></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Muzzle Velocity:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">2550.0 ft/s</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Distance to Chronograph:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">10.0 ft</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Sight Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1.50 in</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Sight Offset:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.00 in</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Zero Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.00 in</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Zero Offset:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.00 in</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Windage:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.000 MOA</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Elevation:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.000 MOA</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Line Of Sight Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.0 deg</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Cant Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.0 deg</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Wind Speed:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">10.0 mph</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Wind Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">90.0 deg</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Speed:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">10.0 mph</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Angle:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">90.0 deg</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">12.0 in</span></td><td class="input_desc_cell" colspan="1"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Temperature:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">59.0 °F</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Pressure:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">29.92 in Hg</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Humidity:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0 %</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Altitude:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.0 ft</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Vital Zone Radius:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">5.0 in</span></td><td class="input_desc_cell" colspan="1"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Std. Atmosphere at Altitude:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Pressure is Corrected:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">Yes</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Zero at Max. Point Blank Range:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Target Relative Drops:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">Yes</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Mark Sound Barrier Crossing:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Include Extra Rows:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Column 1 Units:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1.00 in</span></td><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Column 2 Units:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1.00 MOA</span></td></tr>
<tr class="input_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial;"><td class="input_desc_cell" colspan="1"><span style="color: #444444;">Round Output to Whole Numbers:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">No</span></td><td class="input_desc_cell" colspan="1"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
<tr class="section_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="section_title_col" colspan="4"><span style="color: #444444;">Output Data</span></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Elevation:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">8.926 MOA</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Windage:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.000 MOA</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Atmospheric Density:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.07647 lb/ft³</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Speed of Sound:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1116.4 ft/s</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Maximum PBR:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">275 m</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Maximum PBR Zero:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">234 m</span></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Range of Maximum Height:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">130 m</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Energy at Maximum PBR:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">1155.8 J</span></td></tr>
<tr class="break_row" style="background-color: #dadada; background-position: initial initial; background-repeat: initial initial; height: 1pt;"><td class="break_cell" colspan="4"></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="input_desc_cell" colspan="1" style="text-align: left;"><span style="color: #444444;">Sectional Density:</span></td><td class="input_value_cell" colspan="1" style="text-align: right;"><span style="color: #444444;">0.205 lb/in²</span></td><td class="input_desc_cell" colspan="1" style="text-align: left;"></td><td class="input_value_cell" colspan="1" style="text-align: right;"></td></tr>
</tbody></table>
<table class="output_table" style="border-spacing: 5pt 1pt; font-size: 9pt; font-weight: 900; width: 100%px;"><tbody>
<tr class="section_title_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 10pt; text-align: center;"><td class="section_title_col" colspan="11"><span style="color: #444444;">Calculated Table</span></td></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Range</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Drop</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Drop</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Windage</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Windage</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Velocity</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Mach</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Energy</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Time</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Lead</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">Lead</span></th></tr>
<tr class="output_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(m)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(in)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(MOA)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(in)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(MOA)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(ft/s)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(none)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(J)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(s)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(in)</span></th><th class="" colspan="1" style="background-color: #cccccc;"><span style="color: #444444;">(MOA)</span></th></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">0</span></td><td class="drop_length_cell"><span style="color: #444444;">-1.5</span></td><td class="drop_angle_cell"><span style="color: #444444;">***</span></td><td class="wind_length_cell"><span style="color: #444444;">0.0</span></td><td class="wind_angle_cell"><span style="color: #444444;">***</span></td><td class="velocity_cell"><span style="color: #444444;">2558.3</span></td><td class="mach_cell"><span style="color: #444444;">2.291</span></td><td class="energy_cell"><span style="color: #444444;">2167.1</span></td><td class="time_cell"><span style="color: #444444;">0.000</span></td><td class="lead_length_cell"><span style="color: #444444;">0.0</span></td><td class="lead_angle_cell"><span style="color: #444444;">***</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">100</span></td><td class="drop_length_cell"><span style="color: #444444;">5.3</span></td><td class="drop_angle_cell"><span style="color: #444444;">4.6</span></td><td class="wind_length_cell"><span style="color: #444444;">1.3</span></td><td class="wind_angle_cell"><span style="color: #444444;">1.1</span></td><td class="velocity_cell"><span style="color: #444444;">2293.0</span></td><td class="mach_cell"><span style="color: #444444;">2.054</span></td><td class="energy_cell"><span style="color: #444444;">1740.9</span></td><td class="time_cell"><span style="color: #444444;">0.135</span></td><td class="lead_length_cell"><span style="color: #444444;">23.8</span></td><td class="lead_angle_cell"><span style="color: #444444;">20.8</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">200</span></td><td class="drop_length_cell"><span style="color: #444444;">4.2</span></td><td class="drop_angle_cell"><span style="color: #444444;">1.8</span></td><td class="wind_length_cell"><span style="color: #444444;">5.4</span></td><td class="wind_angle_cell"><span style="color: #444444;">2.3</span></td><td class="velocity_cell"><span style="color: #444444;">2044.5</span></td><td class="mach_cell"><span style="color: #444444;">1.831</span></td><td class="energy_cell"><span style="color: #444444;">1384.0</span></td><td class="time_cell"><span style="color: #444444;">0.287</span></td><td class="lead_length_cell"><span style="color: #444444;">50.5</span></td><td class="lead_angle_cell"><span style="color: #444444;">22.1</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">300</span></td><td class="drop_length_cell"><span style="color: #444444;">-7.0</span></td><td class="drop_angle_cell"><span style="color: #444444;">-2.0</span></td><td class="wind_length_cell"><span style="color: #444444;">12.8</span></td><td class="wind_angle_cell"><span style="color: #444444;">3.7</span></td><td class="velocity_cell"><span style="color: #444444;">1811.3</span></td><td class="mach_cell"><span style="color: #444444;">1.622</span></td><td class="energy_cell"><span style="color: #444444;">1086.3</span></td><td class="time_cell"><span style="color: #444444;">0.457</span></td><td class="lead_length_cell"><span style="color: #444444;">80.5</span></td><td class="lead_angle_cell"><span style="color: #444444;">23.4</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">400</span></td><td class="drop_length_cell"><span style="color: #444444;">-30.9</span></td><td class="drop_angle_cell"><span style="color: #444444;">-6.7</span></td><td class="wind_length_cell"><span style="color: #444444;">24.2</span></td><td class="wind_angle_cell"><span style="color: #444444;">5.3</span></td><td class="velocity_cell"><span style="color: #444444;">1590.9</span></td><td class="mach_cell"><span style="color: #444444;">1.425</span></td><td class="energy_cell"><span style="color: #444444;">838.0</span></td><td class="time_cell"><span style="color: #444444;">0.651</span></td><td class="lead_length_cell"><span style="color: #444444;">114.5</span></td><td class="lead_angle_cell"><span style="color: #444444;">25.0</span></td></tr>
<tr class="data_row" style="background-color: #f0f0f0; background-position: initial initial; background-repeat: initial initial; text-align: center;"><td class="range_cell"><span style="color: #444444;">500</span></td><td class="drop_length_cell"><span style="color: #444444;">-71.3</span></td><td class="drop_angle_cell"><span style="color: #444444;">-12.5</span></td><td class="wind_length_cell"><span style="color: #444444;">40.6</span></td><td class="wind_angle_cell"><span style="color: #444444;">7.1</span></td><td class="velocity_cell"><span style="color: #444444;">1383.0</span></td><td class="mach_cell"><span style="color: #444444;">1.239</span></td><td class="energy_cell"><span style="color: #444444;">633.3</span></td><td class="time_cell"><span style="color: #444444;">0.872</span></td><td class="lead_length_cell"><span style="color: #444444;">153.5</span></td><td class="lead_angle_cell"><span style="color: #444444;">26.8</span></td></tr>
</tbody></table>
</center>
</td></tr>
<tr><td><table class="credit_table" style="border-spacing: 5pt 1pt; font-size: 8pt; font-weight: 900; width: 100%px;"><tbody>
<tr class="credit_row" style="background-color: #dddddd; background-position: initial initial; background-repeat: initial initial; font-size: 8pt; text-align: right;"><td class="credit_cell"><span style="color: #444444;">10/11/13 18:24, <a href="http://www.jbmballistics.com/">JBM</a>/<a href="http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi">jbmtraj-5.1.cgi</a></span></td></tr>
</tbody></table>
</td></tr>
</tbody></table>
</blockquote>
<br />
<div>
We can see the top chart refers to 5.56mm M855 from a 16" barrel, and the bottom to 6.8 SPC from the same length barrel firing <a href="http://196800revolutionsperminute.blogspot.com/2012/11/where-do-i-get-my-ballistic-coefficient.html">110 gr Hornady BTHP bullets.</a> Higher velocities have been achieved by 6.8 SPC from this barrel length, but not - to my knowledge - with factory ammunition.<br />
<br /></div>
<div>
6.8 SPC does offer 56% more energy at half a kilometer than 5.56mm (not <a href="http://www.youtube.com/watch?list=UUZ-qxagOkAmCEP-Tu6YliUQ&v=UVXJBLuxwZI&feature=player_detailpage#t=479">three or four times as much energy,</a> as I've heard it claimed more than once), but what is that per kilogram? M855 weighs about 12 grams and provides about 34 kilojoules of energy at 500m per kilogram of ammunition carried. 6.8 SPC weighs about 17 grams with a 110 grain bullet, and provides about 37 kilojoules of energy at 500m per kilogram, ten percent more than M855. Is a 25% worse trajectory, increased bolt stress, lower reliability, fewer rounds per magazine, and the introduction of an entirely new cartridge worth a 10% increase in energy per kilogram at half a kilometer? Keep in mind that, due to its large case, good sectional density, and fairly high velocity, the 6.8 SPC is one of the best performers in this category of ammunition.<br />
<br />
<br /></div>
<div>
The third category contains cartridges that either have never been made or are not what they are advertised to be. Examples include the 6mm Optimum, Mr. Williams' 6.5/8/800, and the 6.5 Grendel. Only one of these actually exists - the 6.5 Grendel. To many, the existence of the Grendel proves the GPC concept's viability, but a closer examination shows that is not the case. There are numerous problems with the 6.5 Grendel, first and foremost being its unsuitability for military applications. Beyond (valid) concerns about the cartridge's extreme shoulder angle and lack of case taper, the case itself does not have enough internal volume to accept tracer or steel-cored armor piercing projectiles, except with the lightest bullets. Thus, it cannot fulfill the role of a GPC, as it is not a suitable military cartridge. Further, the 6.5 Grendel provides <a href="http://www.hornady.com/store/6.5-Grendel-123-gr-SST/">low levels of performance with factory loads,</a> only achieving its much-touted velocity and trajectory with delicately loaded handloads using very slow-burning and often compressed powders. For field purposes, it is a 7.62x39 with better bullet selection.<br />
<br />
Enter the 6.5/8/800, the hypothetical "ideal" general-purpose cartridge proposed by Mr. Williams in his opus. Is this cartridge feasible, and if so, does it offer enough of an advantage to ISAF/NATO members to warrant its adoption and the retirement of both the 7.62 and 5.56 calibers? Mr. Williams' has only provided us with with visual mockups of his cartridges via his website, so the only way to find out is to design the cartridge for him. As per his requirements, the cartridge will be 6.5mm caliber, have an 8 gram bullet, and produce a muzzle velocity of 800 meters per second from a 20" barrel.<br />
<br />
Using a combination of CAD modelling and <a href="http://kwk.us/powley.html">this online Powley Computer,</a> I created a virtual cartridge that met these specifications, so that we can see if it might be a suitable replacement for 5.56mm and 7.62mm.<br />
<br />
The first hurdle to jump was the design of the bullet. Mr. Williams specifies that the bullet should be based on the 7N6 projectile of the Russian 5.45x39 cartridge, which would meet both the good form-factor and lead free requirements. However, simply scaling that projectile up yields a bullet weight of only 5.9 grams (less if it is constructed without any lead at all, as the 7N6 incorporates a lead sleeve and plug), far short of the 8 gram requirement. In the end, I designed my own lead-cored bullet, based on the 7N6, to meet the weight requirement, which came to an overall length of 33.5 millimeters, or 1.32 inches for the imperial-unit Powley Computer. One could also use the existing 123 grain Lapua Scenar and get much the same results, since that projectile is 1.295 inches (32.9mm) long. One final note on projectiles: Because of its heavy, high form factor bullets, the GPC already devotes much of its internal and external volume to accommodating the projectile, which, even lead-cored, is already 13% longer than M80 ball's projectile. The lead-free armor-piercing and tracer projectiles necessitated by the cartridge's military application will only aggravate this problem, and may result in the cartridge's weight spiraling significantly to maintain performance. While Mr. Williams does acknowledge this problem, he does not make any attempt to address it.<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-kjGkoGKEazo/UHGAjkLNk5I/AAAAAAAABEk/pJ1g-GpaXKk/w530-h548-no/GPCCaseDimensions.png" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://2.bp.blogspot.com/-kjGkoGKEazo/UHGAjkLNk5I/AAAAAAAABEk/pJ1g-GpaXKk/w530-h548-no/GPCCaseDimensions.png" height="320" width="309" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 1: The case of the 6.5x50mm GPC, with dimensions</td></tr>
</tbody></table>
<br />
Next, I had to design the case (Fig 1). This was to be a challenge, as utilizing the .30 Remington case (also used by the 6.8 SPC, and favored by Mr. Williams) proved unfeasible due to excessive length needed to attain the requisite performance while maintaining <a href="http://196800revolutionsperminute.blogspot.com/2012/11/case-taper-in-military-cartridges.html">adequate case taper and shoulder angle</a> (.8 and 20 degrees, respectively). I turned instead to the 7.62x45mm Czech for the case head, and attained a case length of 50mm before the performance goals were met. The cartridge now fit within the requisite 2.8" (71.1mm) overall length of 7.62 NATO, and with 45 grains water (2.92 mL) case capacity, was capable of propelling its projectile to 800 m/s within 57,000 PSI (390 MPa) peak pressure, from a 20" barrel (Fig 2).<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-L1WQuVO01Jc/UHGAknTKiDI/AAAAAAAABE0/PNufCUM-5_0/w836-h454-no/GPCPerformance.png" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://3.bp.blogspot.com/-L1WQuVO01Jc/UHGAknTKiDI/AAAAAAAABE0/PNufCUM-5_0/w836-h454-no/GPCPerformance.png" height="345" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 2: The data entered into the Powley Computer</td></tr>
</tbody></table>
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-4knA8uZmteg/UHGWyBJteiI/AAAAAAAABFk/dfyF6LmvD9I/w459-h410-no/6.5x50GPC.bmp" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://2.bp.blogspot.com/-4knA8uZmteg/UHGWyBJteiI/AAAAAAAABFk/dfyF6LmvD9I/w459-h410-no/6.5x50GPC.bmp" height="285" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fig. 3: The completed GPC</td></tr>
</tbody></table>
<br />
<br />
<br />
With the case and projectile finished, and the specified performance achieved, all that was left was to weigh the cartridge and calculate its recoil. The volume of the brass case was 1.109 cm^3, resulting in a weight of 9.43 g. The weight of the powder charge was 2.35 g (36.3 grains), and the bullet, of course, was 8 grams. To calculate the weight of a large rifle primer, I set five together on my powder scale, weighed them, and averaged the result, which was approximately .35 g. When summed, the 6.5x50/8/00 weighed 20.13 grams; more than two grams heavier than Mr. Williams' initial estimate, and nearly 70% heavier than 5.56mm.<br />
<br />
To fully evaluate the cartridge, it was necessary to calculate its recoil energy. The correct formula for this is as follows:<br />
<br />
<br />
<blockquote class="tr_bq">
<b>mB</b> = mass of bullet in kilograms </blockquote>
<blockquote class="tr_bq">
<b>mP</b> = mass of powder in kilograms </blockquote>
<blockquote class="tr_bq">
<b>vB</b> = velocity of bullet at muzzle in m/s </blockquote>
<blockquote class="tr_bq">
<b>vP</b> = velocity of powder gas at muzzle m/s </blockquote>
<blockquote class="tr_bq">
<b>mF</b> = mass of the firearm in kilograms </blockquote>
<blockquote class="tr_bq">
<b>mC</b> = impulse of the cartridge, in kilogram-meters per second </blockquote>
<blockquote class="tr_bq">
<b>eF</b> = energy of the firearm, in joules </blockquote>
<br />
The impulse of a cartridge can be expressed as:<br />
<blockquote class="tr_bq">
<b>mC = mB * vB + mP * vP</b> </blockquote>
<br />
and its energy when fired from a firearm of a certain weight as:<br />
<blockquote class="tr_bq">
<b>eF = [(-mC)^2]/2mF</b></blockquote>
<br />
The velocity of the propellant gases of modern small arms rifle cartridges is described <a href="http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA391847">as being about 4,000 ft/s (1,220 m/s) in this paper from the end of WWII.</a> Using this value, <a href="http://196800revolutionsperminute.blogspot.com/2012/11/how-much-do-rifles-actually-weigh.html">4kg for the weight of the rifle,</a> the values calculated for the 6.5x50/8/800 above, and 1.69 and 2.92 grams for the charge weights of the M855 and M80 ball, respectively, we can calculate the recoil energy of the GPC, 5.56, and 7.62, for comparison:<br />
<br />
<blockquote class="tr_bq">
<b>5.56x45 M855:</b> <b>5.9 kg-m/s</b> impulse, <b>4.3 J</b> energy</blockquote>
<blockquote class="tr_bq">
<b>7.62x51 M80:</b> <b>11.5 kg-m/s</b> impulse, <b>16.7 J</b> energy</blockquote>
<blockquote class="tr_bq">
<b>6.5x50/8/800:</b> <b>9.3 kg-m/s</b> impulse, <b>10.7 J</b> energy</blockquote>
<br />
With two and a half times the recoil energy of 5.56, and over one and a half times as much impulse, it's doubtful that it could be an effective replacement for that cartridge in all but the heaviest small arms. While this level of recoil is not too far outside Mr. Williams' initial estimates, I contend that they do not allow the cartridge to be chambered in the light, small, carbines that are now popular, especially in echelon roles. Therefore, the GPC cannot effectively replace 5.56mm.<br />
<br />
While this all may sound very negative, there is a silver lining: the cartridge produced about a 20% superior trajectory to 7.62 at 1,000m, along with providing about 15% additional energy at that range with significantly reduced recoil energy. Indeed, while overweight, and having excessive recoil, the cartridge seems superior to 7.62mm in most respects.<br />
<br />
<br />
Since we have designed a cartridge that meets our performance requirements, and we have some idea of how much it weighs, how would replacing 5.56 and 7.62 with it affect the burden of the infantry platoon? Using the figures from <a href="http://thedonovan.com/archives/modernwarriorload/ModernWarriorsCombatLoadReport.pdf">this report on infantry combat loads,</a> we can get some idea.<br />
<br />
The infantry platoon in the US Army contains three infantry squads, a weapons squad, and a platoon headquarters.<br />
<br />
In each of the three infantry squads, there is the Squad Leader armed with an M4 Carbine, two Team Leaders armed with M4 Carbines, two Automatic Riflemen armed with M249 SAWs, two Grenadiers armed with M4 Carbines and attached M203 GLs, and two Riflemen armed with M4 Carbines.<br />
<br />
<blockquote class="tr_bq">
Weight of ammunition (only, not including magazines or links) of infantry squad breakdown by squad role: </blockquote>
<blockquote class="tr_bq">
Squad Leader: 210 rounds 5.56mm, totaling 2.54 kg<br />
Team Leader: 210 rounds 5.56mm in magazines, 200 rounds linked 5.56mm for M249 totalling 4.96 kg (x2)<br />
Automatic Rifleman: 800 rounds linked 5.56mm, totaling 9.68 kg (x2)<br />
Grenadier: 210 rounds 5.56mm in magazines, 200 rounds linked 5.56mm for M249 totaling 4.96 kg (x2)<br />
Rifleman: 210 rounds 5.56mm in magazines, 200 rounds linked 5.56mm for M249 totaling 4.96 kg (x2) </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of infantry squad: 51.7 kg (x3)</b> </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of infantry squad with 20 gram GPC: 85.4 kg (x3)</b> </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of infantry squad with M240s in place of M249s: 85.5 kg (x3)</b></blockquote>
<br />
In the weapons squad, you have the Squad Leader armed with an M4 Carbine, two Machine Gunners armed with M240 GPMGs, two Assistant Gunners armed with M4 Carbines, and two Ammunition Bearers armed with M4 Carbines.<br />
<br />
<blockquote class="tr_bq">
Weight of ammunition (only, not including magazines or links) of weapons squad breakdown by squad role: </blockquote>
<blockquote class="tr_bq">
Squad Leader: 210 rounds 5.56mm, totaling 2.54kg<br />
Machine Gunner: 300 rounds linked 7.62mm, totaling 7.26 kg (x2)<br />
Assistant Gunners: 210 rounds 5.56mm in magazines, 400 rounds linked 7.62mm for M240 totaling 12.22 kg (x2)<br />
Ammunition Bearer: 210 rounds 5.56mm in magazines, 300 rounds linked 7.62mm for M240, 140 rounds 7.62mm in magazines totaling 13.2 kg (x2) </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of weapons squad: 64.5 kg</b> </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of weapons squad with 20 gram GPC: 63.8 kg</b></blockquote>
<br />
In the platoon headquarters, you have the Platoon Leader armed with an M4 Carbine, the Platoon Sergeant armed with an M4 Carbine, the Radio Operator armed with an M4 Carbine, the Combat Medic armed with an M4 Carbine, and the Field Artillery Forward Observer, also armed with an M4 Carbine.<br />
<br />
<blockquote class="tr_bq">
Weight of ammunition (only, not including magazines or links) of platoon headquarters breakdown by squad role </blockquote>
<blockquote class="tr_bq">
Platoon Leader: 210 rounds 5.56mm, totaling 2.54 kg<br />
Platoon Sergeant: 210 rounds 5.56mm, totaling 2.54 kg<br />
Radio Operator: 210 rounds 5.56mm, totaling 2.54 kg<br />
Combat Medic: 210 rounds 5.56mm, totaling 2.54 kg </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of platoon headquarters: 10.2 kg</b> </blockquote>
<blockquote class="tr_bq">
<b>Weight of ammunition of platoon headquarters with 20 gram GPC: 16.8 kg</b> </blockquote>
<blockquote class="tr_bq">
</blockquote>
<blockquote class="tr_bq">
<b>Total weight of ammunition in the platoon: 229.3 kg</b> </blockquote>
<blockquote class="tr_bq">
<b>Total weight of ammunition in the platoon with 20 gram GPC: 336.8 kg</b> </blockquote>
<blockquote class="tr_bq">
<b>Total weight of ammunition in the platoon with M240s in place of M249s: 330.9 kg</b> </blockquote>
<blockquote class="tr_bq">
<b>Weight increase in the platoon if Carl Gustafs are issued in place of 60mm mortars: 47.5 kg</b></blockquote>
<br />
It is clear that replacing both 5.56 and 7.62 with a cartridge meeting the specifications of Mr. Williams' GPC, as much as that is possible, increases the weight of ammunition of the platoon well above the threshold of other more cost-effective solutions. In addition, 30 out of 38 personnel in the platoon are armed with M4 Carbines. If a GPC were adopted to replace 5.56, those rifles and magazines would have to be supplanted with larger weapons and ancillaries compatible with the new cartridge, adding further weight to the platoon. If being out-ranged is a major concern, issuing more 7.62mm caliber M240 machine guns in place of 5.56mm caliber M249s is a much more cost-effective solution than a complete conversion to a GPC cartridge, while having a similar increase in the weight carried by the platoon. If the problem lies with an inability to use mortars due to restrictive rules of engagement, it would be lighter to issue Carl Gustaf recoilless rifles as direct-fire assets in their stead, than to issue rifles and machine guns chambered for a GPC.<br />
<br />
In conclusion, the GPC concept is one that is attractive only on paper. When rigor is applied, the cost of such re-armament in dollars, hours, and pounds is not justified by the new cartridge's performance. Mr. Williams' proposed cartridges utilizing the .30 Remington and 6.5 Grendel cases are unfeasible as they are conceived, and a cartridge resulting from his performance requirements is too heavy and has too much recoil to replace 5.56mm for most applications. The expectation that he could design a cartridge that produced the same performance as the 6.5mm Arisaka but with much lower weight and sized proved unreasonable. These sorts of errors are understandable, as Mr. Williams does not, to my knowledge, have experience loading ammunition.<br />
<br />
A final note: Mr. Williams' intentions are good, but his concept seems to rely on an overly optimistic estimation of what infantrymen are capable of in terms of marksmanship at range. He thus perceives infantrymen armed with more powerful, longer-ranged rifles as having greater capability than those armed with 5.56mm carbines, when in fact, for the vast majority, the heavier cartridge and necessarily heavier rifles and magazines merely increase their burden. In short, giving long-range rifles to line infantrymen without additional training is a waste of strategic resources, money, and time. This is not to say that specialized marksmen would not be able to take advantage of such a cartridge, but they would be better served by a specialized rifle firing a cartridge with higher velocity and better hit probability at range, not the inherently compromising GPC.</div>
Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com50tag:blogger.com,1999:blog-5557913977913148366.post-75757990377199845552013-10-23T18:08:00.003-07:002013-10-24T00:55:08.772-07:00Small Caliber, High Velocity Isn't NewThere are some old fudder dudders who firmly believe that 5.56x45, .223, and similar and related calibers are a "fad" or a "failed experiment", especially for military use. Usually, they advocate a return to the full-power .308/7.62mm caliber as the end-all caliber, but some advocate for weaker calibers, like 6.8 SPC or 7.62x39. To all those who object, <a href="http://196800revolutionsperminute.blogspot.com/2013/02/the-cult-of-caliber.html">caliber</a> is an important design consideration.<br />
<br />
This post will be short: 5.56 and other small-caliber, high-velocity (SCHV) cartridges are not a fad. In fact, guns have been getting smaller and smaller in caliber, and higher and higher in velocity, for hundreds of years.<i> </i>Let's take a look at how infantry small arms have progressed in the 800 years or so that they've been around. (The historical overview section of this article is only intended as a cursory overview of the weapons in question. Details may have been omitted, glossed over, or compressed. <b>I highly recommend seeking out further literature on these topics.</b>)<br />
<br />
1994 M4 Rifle, 62 gr .224" cal spitzer boat tail at approx 3,000 ft/s<br />
1967 M16A1 Rifle, 55 gr .224" cal spitzer boat tail at approx 3,270 ft/s<br />
1958 M14 Rifle, 147 gr .308" cal spitzer boat tail at approx 2,750 ft/s<br />
1903 (1906) Springfield, 172 gr .308" cal spitzer boat tail at approx 2,640 ft/s<br />
1903 Springfield, 220 gr .308" cal round nose at approx 2,300 ft/s<br />
1892 Krag-Jørgensen Springfield, 220 gr .308" cal round nose at approx 2,000 ft/s<br />
1873 Springfield Rifle-Musket, 405 gr .45" cal lead round nose at approx 1,350 ft/s<br />
1868 Springfield Rifle-Musket, 450 gr .50" cal lead round nose at approx 1,250 ft/s<br />
1853 Enfield Rifle-Musket, 530 gr .577" cal Minié ball at approx 900 ft/s<br />
1700s "Kentucky" Long Rifle, ~140 gr .45" cal round ball at approx 1,500-2,000 ft/s<br />
1717 Charleville Musket, 494 gr .69" cal round ball at approx 900 ft/s<br />
<a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CEIQFjAC&url=http%3A%2F%2Fgladius.revistas.csic.es%2Findex.php%2Fgladius%2Farticle%2Fdownload%2F8%2F8&ei=v9SKUe22G8Xy0QHrvoCgCQ&usg=AFQjCNHtlY5aLGMh8_7pF9ZRQv_cL_00LA&sig2=Nf-YYhGqIeQECI9m7M2YwA&bvm=bv.46226182,d.dmQ">16th Century Arquebus,</a> 464 gr ~.68" cal round ball at approx 1,500 ft/s<br />
<a href="http://www.musketeer.ch/blackpowder/handgonne.html">14th Century Hand Gonne,</a> 430 gr .66" cal round ball at approx 1100 ft/s<br />
<br />
From the 18th century onward, we see a trend of ever-increasing muzzle velocity and decreasing caliber. The introduction of paper cartridges containing Minié balls allowed the use of rifle-muskets as standard infantry small arms, as they combined the ease of loading of a musket with the accuracy and range of a rifle. The introduction of the Minié ball also saw a reduction in caliber: from .69" to .58", with a slight increase in projectile weight. This resulted in much greater sectional density, which contributed to the greatly improved ballistic performance of the new rifle-muskets. Additional tests after the American Civil War showed that .50" and later .45" calibers offered even more improved performance. Eventually, .45" caliber metallic cartridges in the form of the .45-70-405 Government would be the standard for the United States for nearly two decades.<br />
<br />
What would replace the breech-loading Springfield rifle-musket would be a smokeless powder foreign bolt action rifle firing a bullet nearly half the weight at nearly half again the muzzle velocity, the 1892 Krag-Jørgensen. The Krag would prove to have a very short service life, being replaced by the superior (and also foreign) Mauser design in the form of the 1903 Springfield rifle, <a href="http://196800revolutionsperminute.blogspot.com/2012/11/30-06-infantry-magnum.html">possessing extremely high performance</a> and a muzzle velocity of 2,300 ft/s. With the implementation of aerodynamic spitzer projectiles in the 1906 rifle, velocity again improved to over 2,600 ft/s, and bullet weight was significantly reduced. The example cartridge used is the M1 Ball load, introduced in 1926, but higher velocity loads like M1906 Ball and M2 Ball were used extensively, both of which fired ~150 gr flat based bullets at 2,800 ft/s. Since the .30-06 cartridge comes in almost endless variations with different bullet weights and velocities, the M1 Ball type used here is intended to be representative of the caliber in general.<br />
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The self-loading era begins with the M1 Garand, also in .30-06, producing performance very similar to that of the Springfield or M14, with a 150 gr flat-based projectile fired at 2,800 feet per second. Because for the purposes of this discussion, it is highly similar to the M14, it has been omitted. After WWII, a program was initiated to develop a lighter magazine-fed select-fire rifle, and resulted, after over a decade of research and testing, in the M14, which was only an incremental improvement over the Garand upon which it is based. The M14, like the Krag before it, would see service as a standard rifle for less than a decade, though it would continue to be used in specialist roles up to the present day.<br />
<br />
The next significant innovation in small arms was what is sometimes called "small-caliber, high-velocity" ammunition, but which in reality was just a continuation of a trend stretching back hundreds of years. US Army studies again suggested that a smaller caliber, lighter bullet, fired at a higher muzzle velocity was desirable, and after a period of development, the resulting 5.56mm cartridge was born, mated to the advanced ArmaLite rifle design. The ArmaLite rifle was unlike previous US Army rifles in many ways, perhaps not the least significant of which was the method of its development. Previous Army designs were developed by Army Ordnance, but the ArmaLite rifle was an independent development by <a href="http://en.wikipedia.org/wiki/Melvin_Johnson">a USMC officer-turned-Army Ordnance Colonel</a> and <a href="http://en.wikipedia.org/wiki/Eugene_Stoner">an aircraft design engineer</a>, in the employ of a division of Fairchild, an aircraft manufacturer. The original AR-10 design, in the same full-power caliber as the M14, competed in the light rifle trials, but was unsuccessful due to the exotic composite barrel, which burst during testing. The later AR-15 design, using the basic principles of the AR-10, but adapted for a much smaller .22" caliber cartridge at the request of Army Field Forces Board No. 3. The combination proved wildly successful, and a derivative design, the shorter M4 Carbine, remains the standard infantry weapon of the United States Army today.<br />
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Jumping backward in time, The "Kentucky" rifles collectively present an outlier, being much higher velocity and smaller caliber than their contemporaries. This was largely due to their tight rifling and sturdy construction, which incidentally made them unsuitable for use as a standard infantry arm, as they could not be loaded quickly. It did however foreshadow the improvements that would be made to rifle performance as rifling, Minié balls, and breechloading mechanisms allowed rifle-muskets to catch up to their civilian rifled cousins. The "Kentucky" rifles do not represent the state of military small arms at the time, but are included for completeness only.<br />
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A very strange anomaly can be seen at the bottom of the table, with both the 16th Century arquebus and 14th Century hand-gonne. Both have higher velocity than the later Charleville musket! Why is this? I do not know for sure, but I suspect that during this period, great emphasis was placed on defeating the personal body armor of the time. To do this would require considerable velocity using the bare lead round ball projectiles of the time. By the 18th century, all that was left of the heavy plate worn by infantry and cuirassiers of the 16th century was the gorget - a decorative neck-guard used as a status symbol. Without the need to penetrate heavy armor, and with no real ability of an individual to hit targets at beyond 20 yards with a smoothbore musket, velocity decreased.<br />
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Since the 18th century, the caliber and projectile weight of small arms have progressively decreased, while the muzzle velocity has progressively increased. The change from 7.62mm caliber rifles to 5.56mm caliber rifles follows this trend, and I expect sometime in the future that the 5.56mm caliber will be obsolesced by something even smaller, lighter, and higher velocity.<br />
<br />
EDIT: Turns out, by pure serendipity, diving through the Weaponsman archives digs up a very similar article they wrote on the exact same subject a while back. <a href="http://weaponsman.com/?p=794">Readers may find it interesting.</a>Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com3tag:blogger.com,1999:blog-5557913977913148366.post-10310976395490321382013-04-11T21:53:00.000-07:002013-04-18T00:21:38.645-07:00What is a clip? What is not a clip?You've just gotten into firearms. It's a new, strange world full of opinions, history, and lots of marketing. You and your friend, who's been into guns for ages, it seems, go to the gun store for a look around. You've just bought a Savage Model 64 a few weeks back, and you've had a hard time finding any of the little ugly black aluminum bits that hold the ammunition. You come up to the gun counter, get the attention of a clerk, and ask:<br />
<br />
<blockquote class="tr_bq" style="text-align: center;">
"Hi, you got any clips for a Savage .22?"</blockquote>
<br />
The clerk groans and rolls his eyes. You look back at your friend, wondering what you did, and he looks a little embarrassed, but he's making a noble effort to hide it. What went wrong?<br />
<br />
Gun owners can be very sensitive about this little quirk of firearm terminology. "Clip" is a flag to many of them that says "I am an idiot; I learned everything I know about firearms from TV, and if you interact with me for any length of time, I will make your day difficult." Sadly, like many people who use the term "clip" to mean "thing you load your gun with", you just want a magazine or two, and to go about your day.<br />
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Well, you can't change gun owners. If you could, no one would use lever actions anymore. Nah, we're all a bunch of sticks in the mud, and often pretty loud about it, too. It's better, trust me, to just play along, and learn the difference between a magazine, and a clip.<br />
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There are <a href="http://www.youtube.com/watch?v=AF21sihEgOU">a number of resources online</a> which aim to teach this difference. All the ones I have seen do not quite reach the mark. I will attempt to give the most concise, but widely-applicable definition that I can.<br />
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<blockquote class="tr_bq" style="text-align: center;">
The term "clip" refers to devices made of (usually) a single piece of stamped and/or bent metal which retains rounds ammunition for the purpose of feeding into a weapon or magazine, and which <b>does not</b> contain a spring for advancing the cartridges to the chamber during cycling.</blockquote>
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Sheesh! That was a mouthful! Why does it have to be that way?<br />
<br />
Clips, almost always, contain springs. From <a href="http://shootersgunaccessories.com/images/ncstpicaakc.jpg">SKS stripper clips,</a> to <a href="http://www.gunblast.com/images/SW-610/DSC02619.jpg">revolver moon clips,</a> it's extremely common for clips to be sprung or contain springs. The important distinction here lies in what the spring <i>does.</i> In virtually all clips I'm aware of, the spring acts to <i>hold the rounds in the clip.</i> In a magazine, the mainspring performs two, or even three functions:<br />
<br />
1. To hold the rounds in the magazine.<br />
<br />
2. To push the next round into the feeding position, after a round has been stripped from the magazine.<br />
<br />
3. (often) To hold the magazine together.<br />
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To this end, the springs in magazines are usually large, coiled wire springs, which are a separate part. Because of these large, dedicated springs, magazines are usually much, much more expensive than clips.<br />
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As if things needed to be more complicated, not all clips are springs, however. <a href="http://candrsenal.com/wp-content/uploads/2012/01/303StripperClip.gif">This .303 British 5-round clip</a> holds its cartridges in primarily by friction. It is somewhat springy, but if you were to polish the inside of the clip to 400 grit, it probably would not hold the rounds in place any more.<br />
<br />
The video by Life, Liberty, Etc claims that "clips are for loading magazines, and magazines are for loading the breech." While this is <i>often</i> true, in many cases it is not. For instance, with revolver moon clips, there is no magazine, and <a href="https://www.usconcealedcarry.com/wp-content/uploads/2012/01/reloading-the-revolver-cover.jpg">the clip holds ammunition in place while it is seated in the chambers,</a> and merely simplify loading and unloading by making the ammunition a single unit. With a Garand en-bloc clip, the ammunition is loaded into the magazine, but <a href="http://www.odcmp.org/0409/images/ComptRulesImg/GarandLoading.jpg">it is the en-bloc clip's feed lips which hold the ammunition in the proper feeding position as it is rammed by the bolt into the chamber.</a> The next round of ammunition is then forced into position by the internal magazine's spring. In this way, the clip and magazine work together as a unit to allow the gun to function.<br /><br />The above is a lot to remember, for anyone. The Life, Liberty, Etc definition is a bit shorter, but it doesn't really help you if you see some nondescript clip-like object at the gun show and want to know if it's a magazine or a clip. Here's perhaps a more helpful mnemonic:<br /><br />
<blockquote class="tr_bq">
"Cheap clips, expensive magazines".</blockquote>
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Clips are almost always simpler, and thus cheaper than magazines. Often, they are downright disposable. It's not uncommon for someone to spend more than $20 on a single magazine, even for used examples, but you might spend $20 on a bag of 50 clips without being branded a thief. The fact that "cheap" and "clip", and "expensive" and "magazine" have the same number of syllables, respectively, should help the reader remember, in general, which is which.<br />
<br />
<br />
There are endless permutations to clips and magazines, some (thankfully, very rare) blurring the line between the two. Hopefully, however, this article has given the reader some insight into which is which, and why gun owners are so anal about the difference between the two.<br />
<br />Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0tag:blogger.com,1999:blog-5557913977913148366.post-4184732484548819902013-02-15T18:45:00.001-08:002014-07-31T16:07:22.537-07:00The Cult of CaliberNearly every American firearms enthusiast has been to a gun store, a gun show, a gun forum, or some other gun-related venue, and heard:<br />
<br />
<blockquote class="tr_bq">
"Yeah, I don't carry a [gun of X type] that isn't in [a specific caliber, a caliber above X arbitrary value, etc]."</blockquote>
<br />
And, if you haven't yet, you will.<br />
<br />
What is it about specific calibers, be it .308 or .45 or something else, that really turns people on? After all, it's just a measurement of one particular area on the projectile. A fetish for bullet mass, or better yet cartridge muzzle energy, would make more sense. Yet, there it is.<br />
<br />
Today I want to address two specific hymns sung by acolytes of the Cult of Caliber, the first being this:<br />
<br />
<blockquote class="tr_bq">
"If a 5.56 round fails to [tumble/fragment/expand], then what you really have is just a glorified .22."</blockquote>
<br />
Variations on this theme appear everywhere, even <a href="http://sadefensejournal.com/wp/?p=778">some well respected defense journals.</a> But something has been bugging me about it.<br />
<br />
The first is, isn't this basically the same as saying "if a 5.56 round hits a target and performs exactly like a .22 LR, then it won't be any more effective than a .22 LR"? It may be true, but besides being a bit disingenuous by singling out 5.56, it doesn't really seem useful, as it doesn't tell us anything about how likely it is that 5.56 will perform like a .22.<br />
<br />
My other objection is that there's nothing special about a <i>caliber.</i> It's just a measurement, either the diameter from <a href="http://7.62x54r.net/MosinID/Bore.jpg">one land to another,</a> the diameter of the grooves, the diameter of the projectile itself, or even just some arbitrary number that's kinda close to one of those measurements. There aren't any caliber-specific performance nodes where one caliber has something special going for it over another.* The statement above frames the situation as if 5.56 has some special quality, that other calibers don't have, which is detrimental to its terminal effectiveness. Even assuming the above statement were <i>true,</i> why would 5.56 be special? Shouldn't the below statement be just <i>as</i> true?<br />
<br />
<blockquote class="tr_bq">
"If a 7.62 round fails to tumble, fragment, or expand, then what you really have is just a glorified .32 ACP."</blockquote>
<br />
.32 ACP from a handgun produces about as much energy as .22 LR from a rifle. It's almost certainly not any more effective. How then, even if the oft-heard statement about 5.56 were true, would it inform us about any deficiency in the cartridge? And if it's <i>not</i> true, why take it seriously?<br />
<br />
A similar, but different quip is also often heard, relating to 5.56's parental history:<br />
<br />
<blockquote class="tr_bq">
"5.56 is based on the .222 Remington, which was intended as a varmint cartridge."</blockquote>
<br />
While it's true that the .222 Remington was and is popular with varmint hunters, <a href="http://www.thegunzone.com/556dw.html">the 5.56 was, with some very explicit supporting evidence, designed specifically as a battle cartridge.</a> Indeed, one could as easily say that the 7.62 is just an overgrown varmint cartridge, it being the same caliber as the .32-20, which was a common caliber for small game in previous years. This quip is a bit more banal, and really isn't based on anything but semantics. A chambering isn't good for only one thing; just because the .222 Remington sees a lot of use as a (long range) varmint cartridge doesn't mean that you couldn't easily kill a person with it, or that it's only effective against varmints. Considering the fact that <a href="https://www.youtube.com/watch?v=pSxv30ToZ8A">varmints are usually dispatched</a> by <i><a href="http://www.saubier.com/forum/showthread.php?t=7749">blowing gigantic holes in them,</a></i> a "varmint" cartridge loaded with appropriate bullets might be a real man-stopper.<br />
<br />
It's simply not appropriate to judge a cartridge by its caliber alone. Caliber is just a measurement; high velocity bullets are not like icepicks; they do not simply poke a hole of their size and shape, even if they don't do anything exotic. For example, here's <a href="https://www.youtube.com/watch?v=_2tkgIdX6ak">a video of a perfectly stable .30 Carbine bullet impacting a block of gelatin</a> and doing some pretty dramatic things to it. This post isn't intended to settle whether 5.56 is a good man-stopper or not once and for all (I was hoping its steady half century of use for that purpose would), but I am hoping I've thoroughly put down those two particular arguments.<br />
<br />
<br />
*This isn't entirely true, as propensity for yaw actually scales with caliber. <a href="http://www.dtic.mil/dtic/tr/fulltext/u2/705381.pdf">Here's a paper describing the phenomenon.</a> However, this assumes homologous bullets, and so you <i>could</i> have a .30 caliber bullet that yaws as easily as a .22 caliber bullet, etc., if they weren't homologous.Nathaniel Fitchhttp://www.blogger.com/profile/15011387972300996469noreply@blogger.com0