Friday, November 30, 2012

Tank Guns: A bit of a tangent

A friend of mine and I were wondering what common tank in WWII had the best ratio of main gun energy to weight, so I made a chart.

How does the P90 compare to other submachine guns?

Quite well, actually.

How much do rifles actually weigh?

Most of what you find online are empty weights of rifles, with no attachments. This is handy, but it doesn't tell you how much weight is actually in the hands of a soldier or marine as he hikes around the mountains of Afghanistan in 2012 or as he pushes towards Berlin in 1945.

Here's a handy chart showing you how much rifles actually weigh.

Where do I get my ballistic coefficient figures?

Mostly from here.

How much does your ammo weigh?

Now you can find out.

The Myth of The .45 ACP

The legendary .45 ACP semiautomatic handgun: Is there any other caliber - gun combination that is so well-regarded? Why are we even bothering to question what is clearly a seasoned, battle-tested cartridge?

Well, as you'll see, with the .45 ACP, not everything is as it seems.

The .45 ACP, as is well-known, was born of a series of tests conducted in 1904 as a result of the Philippine Insurrection, popularly called the "Thompson-LaGarde Tests". Here is a fair account of the tests, and most of my discussion of the tests will be based around that article.

Most proponents of the .45 ACP and the 1911 handgun know of only the conclusions of the test, repeated here for convenience:

"the Board was of the opinion that a bullet, which will have the shock effect and stopping effect at short ranges necessary for a military pistol or revolver, should have a caliber not less than .45″

However, this conclusion was not then, and is not now, any evidence at all in the discussion of handgun calibers. As I will enumerate, the testing procedures were deeply flawed, so much so that virtually no conclusions at all can be drawn from the tests with regards to handgun ammunition effectiveness.

My first concern is with the types of projectiles used. We have in the tests two primary types of projectiles: Full metal jacket projectiles, that is lead clad with a thick layer of (usually) copper alloy, and cast lead projectiles, which are just a lead bullet, with no cladding. The jacketed projectiles included the 7.65mm Luger, .38 ACP, and 9mm Luger. The cast lead projectiles included the .476 Eley, .38 Long Colt, .45 Long Colt, and .455 Webley (called the .455 Man Stopper in the tests). The only unjacketed lead projectile representing the small caliber cartridges is the extremely impotent .38 Long Colt, which produces less than two-thirds the energy of 9mm Luger, and even less than the modern .38 Special. So do the unjacketed lead projectiles give their respective cartridges an edge? No one knows, because the Thompson-LaGarde tests didn't bother to control for it. What you can say is that the .45 Long Colt, .476 Eley, and .455 Webley were only fairly compared in this regard with the .38 Long Colt, which is much less powerful than any of those cartridges.

The rotten core of the tests goes beyond that, however. The tests used bovines as their targets, which are not representative of a human being. In fact, a cartridge that may be a wonderful man-stopper may be a terrible cow-stopper, and vice-versa, because the primary disruption of tissue may occur much earlier than is required to quickly dispatch a cow, but at just the right time to eliminate a human threat. A human torso typically does not exceed a foot and a half even at its broadest measurement from armpit to armpit, but a normal cow's width at the heart is around 20"+. Thus, the optimum distance for a bullet to disrupt to incapacitate a man is essentially as early as possible, while for bovines a bullet that expands very early may not reach the vital organs. In addition, the testers were most concerned with how long it took the animals to die, not whether the animal was dropped immediately, or continued to be lively until the time of death.

To further invalidate any conclusions the testers may have drawn, the shooting procedure was completely uncontrolled. Instead of shooting the cattle in a controlled fashion, keeping the number of rounds and locations hit constant between rounds, the testers simply shot at the animals at their leisure, recording the results regardless of whether the weapon jammed or worked perfectly, or whether they hit what they were aiming for or not. The testers also seem to disregard several of their results which ran contrary to the "bigger calibers are better" conclusions, such as the stag which was shot twice with a .476 Eley and was alive and on its feet for four minutes afterward, only to die after five minutes, or the stag that was shot once with a 7.65 Parabellum, and died within 30 seconds, or the bull that took twelve .455 shots to put down. To make matters worse, only 13 animals total were killed, with all calibers, which gives us a sample size of worse than 2 animals per caliber (some were fired at three animals, some at two, some at only one).

As if to add insult to injury, Thompson and LaGarde performed one final test: They hung the cadavers of the animals they killed previously from the rafters of a barn, and measured the sway of a cadaver as they shot at it. No standard was used against which all rounds were tested, and no measurements were taken, the testers simply looked at the sway of the cadaver and assigned it an arbitrary number value.

In short, the tests were a mess, and no conclusions whatsoever can be drawn from their data. The article asserts that Thompson and LaGarde's famous conclusion (which, by the way, includes an addendum that all but admits that all pistol rounds are terrible stoppers, and that the best way to stop a foe is to pour lots of fire into him quickly) was the product of soldierly duty, rather than conviction, that they felt the need to come up with some answer, rather than return empty handed. I cannot speak to this. However, the fact that the tests have been used for over a century as evidence of the great stopping power of large-caliber rounds is a travesty to anyone with a scientifically inclined mind.

The fact that the tests were a complete bust does not prove that the .45 ACP sucks, but a fairly cursory examination of the cartridge alongside its stablemates does pale it in comparison.

First, let's address something that is often repeated on the Internet and at gun shows and in gun stores nationwide: "The .45 ACP is a much better stopper than 9mm, because it is much more powerful."

But is it, really?

Well, first, "power" is a scientific term referring to the rate at which energy is transferred, but what the gun show John Brownings are really referring to is energy. Which cartridge has more energy, 9mm, or .45?

Well, they're about even, actually.

A standard 9mm load produces about 1,200 ft/s with a 115gr bullet from a 5" barrel. This is pretty common performance for training or FMJ loads at standard pressure. Since the English system is all whacked, we're going to convert these figures to metric before we do the energy calculation (trust me, it's easier this way):

1,200 ft/s / 3.28 ft/m = 367 m/s

115 gr / 15.43 gr/gm = 7.45 gm

Naturally, the equation for energy is one half mass times velocity squared:

.5 x 7.45 gm x (367 m/s)^2 = 499 J

A standard .45 ACP ball load, for comparison, produces around 850 ft/s with a 230 gr bullet from a 5" barrel:

850 ft/s / 3.28 ft/m = 259 m/s

230 gr / 15.43 gr/gm = 14.91 gm

.5 x 14.91 gm x (259 m/s)^2 = 501 J

Source: Hodgdon, using WSF powder.

That's right, standard pressure 9mm ball loads are pretty much directly comparable in energy with standard-pressure .45 ACP loads. Now, sometimes you'll see cheaper plinking loads that produce less velocity, and often 9mm is shot from 4" barrels, where .45 is normally shot from 5" barrels, but in an apples-to-apples comparison, they're about the same.

But why? The .45 is much larger, surely it should be more powerful. Yes, but the .45 ACP is much lower pressure (circa 22,000 PSI) versus the 9mm (circa 32,000 PSI), which accounts for its pretty mediocre performance.

OK, fine, but what about lighter weight .45 loads? That's what most people use for self-defense, the 185 gr JHP +P of whatever name brand, right? OK, sure, but to make sure it's a fair comparison, we'll compare it to the 9mm +P. I'm taking my data from BallisticsByTheInch so that there can be no question of the sources.

9mm Luger 115gr JHP +P from Corbon, 5" barrel:

1,372 ft/s or 418 m/s

115 gr or 7.45 gm

.5 x 7.45 x (418^2) = 652 J

.45 ACP 185gr JHP +P from Corbon, 5" barrel:

1,149 ft/s or 350 m/s

185 gr or 11.99 gm

.5 x 11.99 x (350^2) = 736 J

Ahah! The .45 ACP pulls ahead with 13% more energy! Well, yes, of course it does, because it is using a shorter bullet than the standard load, allowing it more case capacity. The 9mm, on the other hand, is using the same weight, and presumably length bullet (if anything, it's longer, because of the hollow point) as the standard load.. BallisticsByTheInch does not provide us with an analogous short-bullet load for 9mm (the 90gr Corbon is using a .380 ACP bullet, seated to the same depth as a 115gr bullet), but such things do exist. Regardless, the 9mm isn't that far behind the .45, even at these cranked-up pressures. However, if that 13% greater output sounds good enough for you, you might want to consider...

The .45 ACP is really, really heavy.

The weight of individual cartridges might not seem like a big deal for a handgun with only a handful of cartridges in the magazine, but consider that the effective handgun is the one you carry around with you all day. A 9mm cartridge with a 115gr bullet weighs about 12 grams, while a .45 ACP cartridge with a 230gr bullet weighs about 21 grams. With a 185gr bullet, the .45 weighs around 18 grams. Even with the lighter ammunition, .45 still weighs 50% more than 9mm, meaning that you have the choice of either carrying fewer rounds, or being saddled with the extra weight. In addition, the .45 ACP is much bulkier, taking up about 60% more volume than 9mm. Is 50% greater weight and 60% greater volume really worth 13% more muzzle energy, and heavier recoiling cartridge? Well, that brings me to...

The .45 ACP has plenty of extra recoil.

Recoil is perhaps the most important aspect of a handgun cartridge in informing how easy it is to shoot. The heavier the recoil of a cartridge, the more time needed to recuperate from a shot, the harder it is to get back on target, and the more you will have to train to become proficient with it. A 9mm standard-pressure cartridge firing a 115gr bullet on 5.7 grains of WSF at 1200 feet/second produces 3.2 kg-m/s recoil impulse and 7.5 J recoil energy, while a .45 standard-pressure cartridge firing a 230gr bullet on 6.4 grains of WSF at 850 feet/second produces 4.4 kg-m/s recoil impulse and 14.0 J recoil energy, or 38% more recoil impulse and 87% more recoil energy! You might say you are willing to handle the extra weight and recoil so you can take advantage of the .45 ACP's additional energy, but that leads me to my next point...

All pistol rounds pretty much suck, regardless of their caliber.

Pistol rounds are right at the edge of what is needed to stop a human being reliably. Few pistol rounds produce over 800J, and most intended for self-defense produce around 200-500J energy. A pistol round may be enough to stop someone by virtue of that person probably not having been shot before, and thus being taken by surprise, but against an undeterred enemy, many, many pistol rounds will most likely be required to stop him. Pistol rounds, whether they be 9mm, .45, .40, or .380 ACP, produce similar wound channels if they have similar bullet construction. FMJ bullets will perform the same typically, more or less regardless of what tissue they hit. They produce a tubular temporary cavity, and a relatively mediocre permanent cavity. Third-generation jacketed hollowpoint bullets, like the Gold Dot or Hydra-Shok are better, but they don't perform the same against bone as they do against soft tissue. But don't despair just yet, for there is hope...

Fourth-generation hollowpoint bullets are pretty good, actually.

Fourth-generation all-copper based bullets, like the Barnes TSX/DPX/TAC-X and the Hornady GMX perform rather well versus bone, and expand to impressive diameters (see the above tests versus bone simulant) in the .7-.8" range. They also tend to hold together better versus harder targets, like wood, steel, aluminum, and glass, instead of falling apart like third-generation bullets. Monolithic copper-based bullets don't have the problem of core-jacket separation, and afford light bullet weights, high velocities, lighter recoil, and good short-barrel performance. Because they are ductile enough to deform, but hold together reliably, they dispense what energy that pistol cartridges do have effectively and consistently throughout their travel in the body. Because of this, they offer an excellent alternative to conventional jacketed hollowpoint bullets in any caliber.

So the .45 ACP performs about as well, or perhaps marginally better than the 9mm against human targets, but at the expense of much greater bulk, weight, recoil, and cost. Is it worth it? No. If you need more punch than 9mm, get a .40.

A Comparison of SCHV Cartridges

The most important aspect of a rifle/caliber combination is how easy it is to hit a target with it. For the cartridge alone, this depends on five factors: Recoil impulse, bullet drop, bullet drift due to wind, time of flight, and the precision with which the cartridge was made. Because military cartridges are usually held to tighter tolerances than most soldiers will be able to take advantage of, in this article we will only take a look at the first four.

Small-caliber, high velocity cartridges are primarily designed to maximize these four characteristics at ranges below five hundred meters. The following analysis is done on six different SCHV cartridges, five which are or have been in service with a major military, and the sixth being an experimental cartridge. For comparison, I will include one intermediate-caliber, medium velocity cartridge, one full-caliber, low velocity cartridge, and the .30 Carbine.

We will examine the recoil impulse of each cartridge, as wells as the drop, drift, and time of flight of each cartridge at 100, 300, and 500m. We will use figures for each cartridge when shot from a 16" barrel, except the 5.56 FABRL, for which the barrel length is unknown to me. Used in this analysis will be's recoil calculator, and JBM's ballistic calculator.

The parameters used in the ballistic calculator are as follows:

Zero Range: 1.0m
Distance to Chronograph: 10.0 ft
Sight Height: 0.00 in Sight Offset: 0.00 in
Zero Height: 0.00 in Zero Offset: 0.00 in
Windage: 0.000 MOA Elevation: 0.000 MOA
Line Of Sight Angle: 0.0 deg Cant Angle: 0.0 deg
Wind Speed: 10.0 mph Wind Angle: 90.0 deg
Target Speed: 10.0 mph Target Angle: 90.0 deg
Target Height: 12.0 in
Temperature: 59.0 °F Pressure: 29.92 in Hg
Humidity: 0 % Altitude: 0.0 ft
Vital Zone Radius: 5.0 in
Std. Atmosphere at Altitude: No Pressure is Corrected: Yes
Zero at Max. Point Blank Range: No Target Relative Drops: Yes
Mark Sound Barrier Crossing: Yes Include Extra Rows: No
Column 1 Units: 1.00 cm Column 2 Units: 1.00 MOA
Round Output to Whole Numbers: No

Let's begin.

5.56x45 M193

Caliber: 5.7 mm
Projectile Weight: 3.56 g
Muzzle Velocity (16" barrel): 960 m/s
Ballistic Coefficient (G7): 0.120
Powder Charge: 1.75 g
Recoil Impulse: 5.96 kg-m/s
Drop 100m: -5.8 cm
Drop 300m: -66.1 cm
Drop 500m: -244.0 cm
Drift 100m: 3.6 cm
Drift 300m: 38.3 cm
Drift 500m: 129.5 cm
Time to 100m: 0.112 s
Time to 300m: 0.397 s
Time to 500m: 0.808 s

5.56x45 M855

Caliber: 5.7 mm
Projectile Weight: 4.00 g
Muzzle Velocity (16" barrel): 900 m/s
Ballistic Coefficient (G7): 0.151
Powder Charge: 1.75 g
Recoil Impulse: 6.14 kg-m/s
Drop 100m: -6.5 cm
Drop 300m: -70.5 cm
Drop 500m: -242.7 cm
Drift 100m: 3.1 cm
Drift 300m: 32.0 cm
Drift 500m: 103.2 cm
Time to 100m: 0.118 s
Time to 300m: 0.404 s
Time to 500m: 0.784 s

5.45x39 7N6

Caliber: 5.6 mm
Projectile Weight: 3.43 g
Muzzle Velocity (16" barrel): 960 m/s
Ballistic Coefficient (G7): 0.168
Powder Charge: 1.40 g
Recoil Impulse: 5.32 kg-m/s
Drop 100m: -5.7 cm
Drop 300m: -59.7 cm
Drop 500m: -198.4 cm
Drift 100m: 2.5 cm
Drift 300m: 25.4 cm
Drift 500m: 80.2 cm
Time to 100m: 0.109 s
Time to 300m: 0.368 s
Time to 500m: 0.699 s

5.45x39 7N22

Caliber: 5.6 mm
Projectile Weight: 3.68 g
Muzzle Velocity (16" barrel): 960 m/s
Ballistic Coefficient (G7): 0.180
Powder Charge: 1.50 g
Recoil Impulse: 5.71 kg-m/s
Drop 100m: -5.6 cm
Drop 300m: -58.8 cm
Drop 500m: -192.3 cm
Drift 100m: 2.3 cm
Drift 300m: 23.5 cm
Drift 500m: 73.2 cm
Time to 100m: 0.109 s
Time to 300m: 0.364 s
Time to 500m: 0.683 s

5.8x42 DBP-10

Caliber: 6.0 mm
Projectile Weight: 4.60 g
Muzzle Velocity (16" barrel): 915 m/s
Ballistic Coefficient (G7): 0.191
Powder Charge (estimated): 1.85 g
Recoil Impulse: 6.89 kg-m/s
Drop 100m: -6.2 cm
Drop 300m: -64.2 cm
Drop 500m: -208.6 cm
Drift 100m: 2.4 cm
Drift 300m: 23.7 cm
Drift 500m: 73.3 cm
Time to 100m: 0.114 s
Time to 300m: 0.380 s
Time to 500m: 0.709 s

5.56x38 FABRL AR-2

Caliber: 5.7 mm
Projectile Weight: 2.40 g
Muzzle Velocity (unknown barrel length): 1,180 m/s
Ballistic Coefficient (G7): 0.126
Powder Charge (estimated): 1.30 g
Recoil Impulse: 4.72 kg-m/s
Drop 100m: -3.8 cm
Drop 300m: -41.2 cm
Drop 500m: -144.0 cm
Drift 100m: 2.4 cm
Drift 300m: 25.2 cm
Drift 500m: 82.9 cm
Time to 100m: 0.090 s
Time to 300m: 0.310 s
Time to 500m: 0.608 s

6.8x43 SPC 115gr FMJ

Caliber: 7.0 mm
Projectile Weight: 7.45 g
Muzzle Velocity (16" barrel): 780 m/s
Ballistic Coefficient (G7): 0.167
Powder Charge: 1.90 g
Recoil Impulse: 8.57 kg-m/s
Drop 100m: -8.7 cm
Drop 300m: -92.9 cm
Drop 500m: -316.9 cm
Drift 100m: 3.5 cm
Drift 300m: 35.4 cm
Drift 500m: 113.7 cm
Time to 100m: 0.136 s
Time to 300m: 0.462 s
Time to 500m: 0.893 s

7.62x39 M43

Caliber: 7.9 mm
Projectile Weight: 8.00 g
Muzzle Velocity (16" barrel): 720 m/s
Ballistic Coefficient (G7): 0.156
Powder Charge: 1.90 g
Recoil Impulse: 8.52 kg-m/s
Drop 100m: -10.2 cm
Drop 300m: -112.1 cm
Drop 500m: -395.9 cm
Drift 100m: 4.2 cm
Drift 300m: 43.4 cm
Drift 500m: 143.4 cm
Time to 100m: 0.148 s
Time to 300m: 0.512 s
Time to 500m: 1.012 s

.30 Carbine Ball M1

Caliber: 7.8 mm
Projectile Weight: 7.13 g
Muzzle Velocity (16" barrel): 580 m/s
Ballistic Coefficient (G1): 0.178
Powder Charge: 0.88 g
Recoil Impulse: 5.41 kg-m/s
Drop 100m: -16.9 cm
Drop 300m: -224.0 cm
Drop 500m: -852.4 cm
Drift 100m: 10.3 cm
Drift 300m: 105.2 cm
Drift 500m: 280.3 cm
Time to 100m: 0.194 s
Time to 300m: 0.749 s
Time to 500m: 1.484 s

.30-06: The Infantry Magnum

I already demonstrated elsewhere that the .30-06 set a suspect trend of low case taper in US military rifle cartridges.

Continuing my War On .30-06, I am also going to provide evidence that the .30-03 Springfield (the .30-06's close ancestor) was a massively overpowered cartridge for the period, and started a trend where cartridges became more powerful than necessary, higher pressure than they had been previously, and higher recoil than is desirable.

Thanks to the magic of Google, I've found powder charge figures for all of the above cartridges, which, coupled with rifle weight figures, gives me the ability to calculate recoil energies for each cartridge/rifle combination. They are listed below the muzzle energy data. Do note that the recoil figures are using rifle-length velocities and weapon weights (to give an idea of how manageable each rifle was), whereas the muzzle energy data is all using approximately 24" barrels (to show how powerful each cartridge was, all things being equal), which was considered carbine length at the time.

Without further ado, I present the .30-03 Springfield, and every major round nosed rifle cartridge in service at that time:

.303 British Mark II
13.9 g (215 grs) bullet on 2.01 g (31.0 grs) cordite at 600 m/s (1,970 ft/s)
2,510 J muzzle energy
15.7 J recoil energy

7.62x54mmR M1891
13.7 g (211 grs) bullet on 2.20 g (34.0 grs) pyroxiline at 615 m/s (2,020 ft/s)
2,610 J muzzle energy
16.7 J recoil energy

.30-40 Army M1894
14.3 g (220 grs) bullet on 2.59 g (40.0 grs) W. A. at 600 m/s (1,960 ft/s)
2,550 J muzzle energy
18.2 J recoil energy

7.9x57mm Patrone 88
14.7 g (227 grs) bullet on 2.55 g (39.3 grs) S-Pulver at 600 m/s (1,970 ft/s)
2,650 J muzzle energy
20.5 J recoil energy

8x50mmR Lebel Balle M
15.0 g (231 grs) bullet on 2.75 g (42.4 grs) Poudre BF at 580 m/s (1,900 ft/s)
2,520 J muzzle energy
19.4 J recoil energy

8x50mmR Mannlicher M.93
15.8 g (244 grs) bullet on 2.75 g (42.4 grs) M.92 at 600 m/s (1,970 ft/s)
2,840 J muzzle energy
25.1 J recoil energy

7x57mm Mauser Modelo 1893
11.2 g (173 grs) bullet on 2.40 g (37.0 grs) nitrocellulose at 670 m/s (2,200 ft/s)
2,520 J muzzle energy
16.0 J recoil energy

6x60mm Lee Navy M1895
8.75 g (135 grs) bullet on 2.14 g (33.0 grs) Rifleite at 730 m/s (2,380 ft/s)
2,310 J muzzle energy
12.2 J recoil energy

.30-03 Springfield M1903
14.3 g (220 grs) bullet on 2.92 g (45.0 grs) W. A. at 700 m/s (2,300 ft/s)
3,510 J muzzle energy
25.5 J recoil energy

That's right, the .30-03 has almost a third again as much muzzle energy and more than 20% more recoil energy than the third-most powerful round-nosed smokeless powder cartridge of the era.

This means that an army training on, say, .303 caliber rifles will have an easier time teaching marksmanship, will have lower re-acquisition times after each shot, and will experience less fatigue during shooting.

Given that during the interwar period and Second World War many nations switched from a softer-shooting rifle cartridge and a longer-ranged machine gun cartridge to issuing the machine gun cartridge for all purposes or switching from a less powerful cartridge to a more powerful one, and that the ubiquitous postwar 7.62x51 NATO was just as powerful as the .30-03 Springfield, I think it can be said that the .30-03 Springfield set off a trend of unnecessary recoil, muzzle energy, and high pressure.

The 8x50R Mannlicher is something of an outlier. It produces similar recoil to the .30-03 cartridge, but far less muzzle energy. Interestingly, it is also the only outlier found in my analysis of case taper in military cartridges. The Austro-Hungarian Empire was fraught with decay and corruption at this point in history, and so it is possible that the development of the 8x50R cartridge was beset by similar demons as could be found in the development of the .30-03 cartridge. It is also possible that Austro-Hungary and the United States were the only two countries that designed their rifle cartridges correctly, but this seems unlikely to me. It is worth noting that the 8x50R Mannlicher does not have greatly higher velocity or sectional density than cartridges such as .30-40 Army, .303 British, or 7.62x54R, but due to its larger caliber (.330") required a heavier bullet and more powder to propel it to speed. The .30-03, in contrast, is faster than its stablemates, by about 350 f/s.

Case Taper in Military Cartridges

I was trying to determine how much case taper was appropriate for military cartridges, but the current standard seems to be "take 5.56/7.62 and copy the taper". Curious as to what effects this method might be having on ammunition design, I did some calculations of my own. What follows is the case taper, in radians, of some of the most popular military rifle cartridges, and some important experimental cartridges, putting an emphasis on those designed prior to WWII.

All data comes from, calculations done by me.

Case Taper of Various Cartridges:

.30-40 Krag: 41.22 Taper Length, .52 Taper Width, .013 Rads Taper
6mm Lee Navy: 40.70 Taper Length, .61 Taper Width, .015 Rads Taper
.30-06: 46.33 Taper Length, .38 Taper Width, .008 Rads Taper
.276 Pedersen: 37.26 Taper Length, .82 Taper Width, .022 Rads Taper
.270 Sidewinder: ? Taper Length, ? Taper Width, .013 Rads Taper
7.62 NATO: 35.77 Taper Length, .21 Taper Width, .006 Rads Taper
5.56 NATO: 33.39 Taper Length, .29 Taper Width, .009 Rads Taper
.300 Winchester Magnum: 50.19 Taper Length, .31 Taper Width, .006 Rads Taper
6mm SAW: 28.36 Taper Length, .25 Taper Width, .009 Rads Taper
6mm PPC: 23.80 Taper Length, .20 Taper Width, .009 Rads Taper
6mm BR: 23.45 Taper Length, .17 Taper Width, .007 Rads Taper
6.8 SPC: 30.05 Taper Length, .25 Taper Width, .008 Rads Taper
6.5 Grendel: 25.60 Taper Length, .14 Taper Width, .005 Rads Taper
7x46mm UIAC: 25.4 Taper Length, .23 Taper Width, .009 Rads Taper

.303 British: 43.84 Taper Length, .75 Taper Width, .017 Rads Taper
.280/30 British: 26.65 Taper Length, .32 Taper Width, .012 Rads Taper

8mm Lebel: 35.00 Taper Length, .96 Taper Width, .027 Rads Taper
7.5x54 MAS: 39.50 Taper Length, .44 Taper Width, .011 Rads Taper

7.92x57: 43.01 Taper Length, .50 Taper Width, .012 Rads Taper
7.92x33: 20.14 Taper Length, .26 Taper Width, .013 Rads Taper

6.5x52 Carcano: 41.00 Taper Length, .28 Taper Width, .007 Rads Taper

8x50R Mannlicher: 36.77 Taper Length, .24 Taper Width, .006 Rads Taper
6.5x54 Mannlicher-Schoenauer: 41.70 Taper Length, .36 Taper Width, .009 Rads Taper

7.62x45 Czech: 32.2 Taper Length, .43 Taper Width, .013 Rads Taper

6.5x55 Swedish: 40.24 Taper Length, .58 Taper Width, .014 Rads Taper

7.5x55 Swiss: 41.12 Taper Length, .51 Taper Width, .012 Rads Taper

6.5x50SR Arisaka: 36.30 Taper Length, .59 Taper Width, .017 Rads Taper
7.7x58 Arisaka: 43.93 Taper Length, .49 Taper Width, .011 Rads Taper

7x57 Mauser: 40.8 Taper Length, .55 Taper Width, .013 Rads Taper

7.62x54R: 38.10 Taper Length, .38 Taper Width, .010 Rads Taper
7.62x39: 27.3 Taper Length, .62 Taper Width, .023 Rads Taper
5.45x39: 26.80 Taper Length, .375 Taper Width, .014 Rads Taper
9x39: 27.49 Taper Length, .34 Taper Width, .012 Rads Taper

5.8x42: 30.27 Taper Length, .53 Taper Width, .017 Rads Taper

The trend revealed here is that, starting with the US .30-06 cartridge (and ignoring the experimental .276 Pedersen), American rifle cartridges have much less case taper than cartridges designed elsewhere. In fact, at the time it was designed, the .30-06 was criticized for being too much like a match cartridge, being too powerful, and in general being an overreaction to the 7mm Mauser.

As you can see, the venerable .30-06 Springfield has case taper comparable to modern benchrest cartridges, like the 6mm PPC and 6mm BR. The 7.62 NATO has even less case taper, while the .223 Remington/5.56 NATO is somewhat less severe in that respect (remember this the next time some .308 fanboy goes on about how the military adopted a benchrest/varminting cartridge). 

Nearly every other foreign military rifle cartridge that saw major service had at least 25% more case taper than the .30-06 Springfield, with the oddball exceptions of the 8mm Mannlicher and 6.5x52mm Carcano.

Given only cartridges designed by foreign militaries after 1945, we can see that case taper has not deviated much from the pre-war standard. Even after the case taper of the 7.62x39 was judged too extreme in the search for its replacement, the cartridges that followed exhibited significantly more case taper than even the 7.62x54R.

Now, no conclusions can be drawn from this. However, suspicions definitely arise concerning the suitability of .008 radian and steeper case taper for military cartridges. The soundness of the design of the .30-06 cartridge is in question, and, though testing would be required to determine if its taper were too severe, the cartridge smacks of something designed as a kneejerk reaction to the much more efficient 7mm Mauser. Almost two decades later, a shorter cartridge with greater taper, much lower recoil, and much less severe bolt thrust and with almost equivalent trajectory and range to M1 Ball was developed in the .276 Pedersen cartridge.

Given that, except in legacy applications, the Russians have abandoned any taper more extreme than .012 radians, and the newest Chinese cartridge has taper of more than .017 radians, it is clear that American case taper standards are overdue for a review. What sort of results might a comprehensive test of case taper turn up? Have American cartridges been inheriting a design flaw present for the past 109 years?

M193 vs. 7N6

5.56x45 M193 and 5.45x39 7N6 Factory Chronograph Velocity and Energy Comparison

Figures used are from the factory chronograph data chart, found here.

Data used includes only "real" M193 and 7N6, all from 16" barrels. Also included is M193 performance from 20 and 14.5" barrels, those being common military barrel lengths.

Lowest Chronograph Averages:
M193 (16"): 941 m/s, 1,578 J (XM193 LC 03)
M193 (20"): 954 m/s, 1,621 J (Q3131A)
M193 (14.5"): 879 m/s, 1,378 J (Q3131A)
7N6 (16"): 946 m/s, 1,534 J (Russian)

Highest Chronograph Averages:
M193 (16"): 976 m/s, 1,698 J (Q3131)
M193 (20"): 998 m/s, 1,777 J (Q3131)
M193 (14.5"): 912 m/s, 1,482 J (XM193)
7N6 (16"): 961 m/s, 1,584 J (Bulgarian)

7N6 trails almost negligibly behind M193 for velocity, in general possessing velocities only up to a percent and a half slower than that of the American cartridge. With its slightly lighter bullet, 7N6 produces between 3-7% less energy than M193, from 16" barrels. Given the Russian cartridge's greatly superior ballistic coefficient (40% higher than that of M193), this small disadvantage in energy can be all but overlooked.

Interestingly, the lauded Q3131A ammunition from Winchester is actually slower, for a given barrel length, than even Russian 7N6 ammunition. Bulgarian 7N6 ammunition, which is fairly common stateside, produces significantly higher velocity, and even more energy than the "gold standard" Q3131A.

This is NOT intended to assert that 5.45 is "better" than 5.56. Whether either cartridge is better than the other is determined by the context in which "better" is relevant. e.g., I consider 5.45 to be a superior cartridge design, but for defensive use, from AR-15s, using civilian ammunition, the .223/5.56 is clearly better (Black Hills doesn't make a Barnes 62gr TSX load for 5.45). However, the widespread opinion that 5.45 is "anemic" compared to 5.56 is wrong, and mostly based on inexpensive civilian 5.45 ammunition, versus hot M193 fired from 20" barrels. All else being equal, the two cartridges are highly comparable.

Welcome to the Gun Research Blog!

There are a lot of basic misconceptions about firearms on the Internet. This blog seeks to do entry-level research to refute a lot of them.

The first several posts on this blog will be ported from my deviantart account, where I first started examining firearms on a public page on the Internet. Many of them do not uphold to the source requirements I intend to keep on this blog from now on, but to the extent that I can, I will try to retroactively source those articles. Nonetheless, they are very educational in general, and are worth including on this blog.