Saturday, January 2, 2016

Frontal Area (Almost) Doesn't Matter For Stopping Power

This is a segment of a comment I made on TFB, preserved here because the argument comes up so damned often:

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:


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.
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?

12 comments:

  1. Very interesting.
    I wonder if this could be tested on a ballistics gel block.
    I'd be especially interested in what happens when fired through several layers of fabric representing somebody wearing a shirt and jacket.
    Would wadcutters prove to be a good defense round? Doesn't seem like that would be true. But I don't know.

    ReplyDelete
    Replies
    1. I recall reading Jim Cirillo's "Guns, Bullets, and Gunfights" where he discussed handloading the rounds he carried on the NYPD Stakeout Squad. IIRC this was in the 1970s and prior to any really functional hollowpoints; wadcutters wete his load of choice in a revolver due to the perceived increase in frontal "cutting surface," and his partner carried a 1911 with the chambered round being a wadcutter, and FMJ in the magazine for feeding reliability.

      Delete
  2. >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.

    Who is "we"? How many gunshot wounds have you observed? Where is the evidence here?

    >In fact, doctors have a difficult time telling them apart, until the bullet is extracted.

    Yeah I've read that on gun forums too. Just because you can't accurately eyeball a difference doesn't mean that there is literally no difference.

    I like how to take a shot at an actual doctor who has dealt with gunshot wounds, as if you are somehow of the same authority because you read gun forums.

    You should stick to surfing the internet, I reckon.

    ReplyDelete
    Replies
    1. Asdsf, actually, you're wrong about that being just gun forum lore. Here are several papers on describing and identifying gunshot wounds by medical doctors; note that they all say that the caliber of the weapon that made the shot must be determined by measuring the bullet itself, not the diameter of the wound, just like I said:

      http://www.tdcaa.com/sites/default/files/page/5%20FRI%20INV%20Molina%20Gunshot%20Wounds.pdf

      "Caliber Determinations
      The caliber of the bullet that caused an entrance in the skin cannot be determined by the diameter
      of the entrance. The size of the hole is due not only to the diameter of the bullet but also to the
      elasticity of the skin and the location of the wound. An entrance wound in an area where the skin
      is tightly stretched will have a diameter different from that of a wound in an area where the skin
      is lax. Similarly, the size of an entrance in bone cannot be used to determine the caliber of the
      bullet that perforated the bone though it can be used to eliminate bullet calibers."

      http://www.archivesofpathology.org/doi/pdf/10.1043/1543-2165(2006)130[1283%3APPOGW]2.0.CO%3B2

      "Generally, bullets are identified by their caliber or diameter
      and whether they have a metal covering or jacketing... A simple ruler
      or caliper is a good way to make this determination with
      a bullet recovered at autopsy."

      http://history.amedd.army.mil/booksdocs/wwii/woundblstcs/

      "The best method of obtaining accurate
      information of this type is to perform an autopsy to locate and identify missiles 4 (fig. 230) and to determine the extent of tissue damage."

      http://www.e-reading.club/bookreader.php/135302/Gunshot_wounds._Practical_aspects_of_firearms,_ballistics,_and_forensic_techniques.pdf

      "The caliber of the bullet that caused an entrance wound in the skin cannot
      be determined by the diameter of the entrance."

      Delete
    2. Nathaniel Fitch, don't you just love when folks read your articles and try to pick them apart and conclude that you are quoting random opinions from internet forums, and insult you at the same time.

      I for one appreciate the time, energy, and dedication you devote to TFB as well as 196,800 RPM. I just found 196,800 RPM today, but judging by this article alone, I will be visiting this website along with TFB quite frequently.

      Delete
    3. Hi Greg,

      Thanks for the positive feedback. In truth, this article is a little half-baked. It is literally a reposted comment from TFB, and needs quite a lot more polish and context to be really good.

      I don't update this blog all that often (though still occasionally), but I do post to TFB daily.

      Thanks for your support!

      Delete
  3. After I shot a 200gr .45acp SWC hand load (ammo I was given, I do not reload), I picked at the tree it stuck in after going through a piece of dryer sheet metal.

    After seeing the nice chunk of metal, I couldnt help wonder if these rounds would be good for defense ammo in certain situations, or hiking, camping situations? That little solid chunk seems like it would do some damage when hitting bone, etc. The only downside I see is for defensive rounds, obviously there would be a certain risk of bystanders being struck. But camping or hiking I can see advantages.

    Also I know this isn't exactly the best source, but pertaining to your discussion, if you have ever seen the TV shows Crime 360, The Shift, and many others, the ballistician always weighs the spent round after it is retreived from the body. I always wondered why they couldn't tell by relative shape, however, bullets shred and lose mass as they come into contact with objects. I always enjoy guessing what round it is when the ballistician or the morgue worker weighs the bullet. "The bullet retrieved from the lower torso is 110 grain s..." - then I blurt out "it was 9mm!" ;)

    ReplyDelete
  4. it would be helpfull if u could put a list with your TFB articles here

    ReplyDelete
    Replies
    1. I have written hundreds of articles for them at this point, so that would be impractical. However, at some point I will try to compile a "Greatest Hits" list for this blog.

      Delete
    2. In the meantime, you can find my entire article archive at this link: http://www.thefirearmblog.com/blog/author/nathaniel-f/

      Delete
  5. i suspect the people who go on insulting rants have probably been drinking.

    ReplyDelete