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But I read on the internet that caliber doesn’t matter

Hypnagogue emails:

Having been called every name in the book for arguing that kinetic energy matters, I suppose I should just leave it to the West Point professor of physics. Turns out pressure wave effects cause rapid incapacitation due to nerve trunk and brain injury above 500 fpe. Serious brain injury (concussion) is likely above 600 fpe.

Here’s the study he references. Quote:

Not all bullet impacts produce a pressure wave strong enough to cause neurological symptoms. The likelihood of a bullet impact remote from the brain leading to rapid incapacitation has been demonstrated to increase with the local pressure wave magnitude.

18 Responses to “But I read on the internet that caliber doesn’t matter”

  1. Don Gwinn Says:

    If that’s true, he’s invalidated the 9mm vs. .45 acp argument, as both are well below that threshold even at the muzzle. Looking at muzzle fpe measurements, it looks like the line for handgun cartridges starts at 10mm and .44 magnum, with the 10mm being kind of iffy.

  2. nk Says:

    The kinetic energy in a bullet is exactly the same as that in your felt recoil. The damage comes from the incompatibility of the kinetic energy’s deleivery device (bullet) with the medium which receives it (flesh, blood and bone), just the same as your gun’s kick (butt/grip against hand/shoulder).

  3. Caleb Says:

    Don beat me to it.

  4. Tomcatshanger Says:

    So 5.56 should be a one shot stop right?

    Or are we talking about pistol caliber energy only, and otherwise we need to use .308 or larger?

    🙂

  5. Loki7154 Says:

    Not necessarily true–look at Doubletap’s .45 ACP +p loadings; 185gr at the muzzle produces over 600 ft-lbs. Buffalo Bore will sell you some .45 Super which will produce almost 700 ft-lbs and can apparently be chambered in a USP or HK45 without a spring change.

    Just saying–there ARE loads of .45 that will get to 500 or 600 ft-lbs (perhaps cheating a bit with the .45 Super, but the Doubletap loads remain). There is only 1 9mm load that I’ve found that will even eek above 500 ft-lbs, and that’s from DT at 511.

  6. Hypnagogue Says:

    A new Springfield auto in .45 Super,
    Or 10 millimeter, a gift from Jeff Cooper
    In a Glock model 20 with upgraded springs;
    These are a few of my favorite things…

  7. Rivrdog Says:

    I call: so what? Do we train to take the one perfect shot, or to keep shooting? There are lots of ways a bullet can kill you, and this newly-defined threshold is only one. BTW, note the use of the owrd “suggest” everywhere in the study. The authors are analyzing anecdotal evidence, and they admit it.

    My favorite defense tactic is still Mozambique. Shred the heart with two rounds and the mid-brain with one, and something tells me that the shootee’s life is measured in maybe only milliseconds less than with a hand-cannon blast.

    Right after Mozambique would be about 5 to the center of mass. After 25 years copping, and during that career, reading every autopsy report I could lay my hands on of every crook who died in a gun battle, I would say that standard police calibers, effectively applied, will do the job every time.

    If you want to put even more aces up your sleeve, get or manufacture a full-silhouette target with the spine imprinted on it, and practice putting your center of mass hits on the spine. No man stands with a severed spinal cord, and most won’t move afterward, either.

    Forget the hand cannons. The gun that saves your bippy is the one you carry and you can hit your target multiple times with.

  8. Hypnagogue Says:

    It’s a bit more than analyzing anecdotal evidence — the authors are statistically testing the hypothesis that a specific traumatic brain injury mechanism demonstrated by experiment in animals can explain rapid incapacitation results in other experiments. They have several similar peer-reviewed papers.

    The pressure-wave traumatic brain injury mechanism is well proven, the question is simply one of measuring it’s significance as a factor in rapid incapacitation.

    If you would like to rebut a professor of physics, have fun. I’ll be watching from over here. http://xkcd.com/675/

  9. Caleb Says:

    Shit, someone should tell all those guys that have been killed with 9mms and .38 Specials that they’re not dead and they should get back up.

  10. Hypnagogue Says:

    Did you read the article? The question is rapid incapacitation, not lethality.

    You’ve got TV tomorrow. Are you sure your head is in the game? You seem dense.

  11. Loki7154 Says:

    Someone should also tell the people killed with .380, .32s, .22s and nail guns that they, too, should get up!

  12. Gun Blobber Says:

    Just to analyze the math a bit, in both the original paper and another by the same authors here, which covers the derivation of the formulas used:

    http://arxiv.org/ftp/physics/papers/0701/0701
    267.pdf

    This paper is cited as [22] in the originally linked article. The results presented work only with expanding, JHP bullets. The formula for pressure on Page 3 of the above linked article is this:

    P = 5E/(d*4*Pi*R^2)

    where E is energy, d is penetration distance, Pi is 3.14… and R is an arbitrary measurement radius from the center of the wound channel. The authors use a 1″ diameter circle, which gives a 0.5″ radius; squared is 0.25 which cancels out the factor of 4 (and yes, inches are the right units to use here, since we need lbs/in^2; however, a measurement in feet, not inches, is required for the “d” variable). (Note, the authors give no justification for the use of a 1″ diameter circle for the measuring point of the pressure wave…. using a 0.5″ diameter circle, or a 2″ diameter circle, could change all of the following numbers by a factor of 4 either way.) Also, things are simplified if we assume penetration of 12″ (1 foot) which works for most common handgun rounds. So the simplified formula is:

    P = 5E/Pi

    The threshold for “likely incapacitation” is given as 1000psi of pressure, which gives a requisite E of 628ft-lbs (200*Pi) under the 12″ penetration assumption, and using the arbitrary 1″ circle.

    Moving on: another key to this formula is the Fudge Factor 5 which shows up in the formula for pressure. This is an estimate of the peak to average pressure ratio for an expanding handgun bullet. They state that “the peak force usually occurs during or soon after expansion, and most bullets have peak to average force ratios between 3 and 8. … Most JHP handgun bullets have a peak to average ratio close to 5.” This is where they get the Fudge Factor 5. Maybe it’s a good estimate, maybe it isn’t. But it probably invalidates the Tokarev anecdote given on Page 4 of the original article (which indeed uses the factor-5 formula — do the math), since military rounds are FMJ and would likely not expand rapidly enough to create the peak pressure of 5x the average pressure.

    In sum, I find these papers little better than the stuff I have seen from the AGW crowd. Some good ideas and reasonable intuition, but when it comes to actually putting solid numbers into formulas, they have to make a few too many assumptions. They end up saying that a bullet penetrating 12″ with 628 ft-lbs (200*Pi) of energy would generate a pressure sufficient to incapacitate, but if the arbitrary measurement diameter of 1″ were changed to half an inch, it would be 157 ft-lbs (50*Pi), and if it were changed to 2″ then the required energy would be 2513 ft-lbs (800*Pi). IMO, it’s all just a little too convenient that they happened to choose a distance that would fall right on the borderline of most handgun rounds. This formula just doesn’t pass the smell test.

    I’m not doubting the pressure theory, or even the 1000psi threshold, since they seem to have solid measurements and good statistical analysis of that stuff; but working backwards from that PSI range to a certain projectile energy just takes things too far. If they were using Metric units, taking pressure in Pa, the choice of 0.0127 meters for the R in their formula would look stupidly arbitrary. A 1″ diameter (1/2″ radius) sounds reasonable and cancels out quickly, but such an unjustified assumption in metric units would be too embarrassing to publish.

  13. Hypnagogue Says:

    That’s a quality comment. Caleb, take note: that’s what smart looks like. Notice the lack of non sequitor and ad hominem arguments.

    Blobber: I think everything you said is absolutely valid — the statistics used are not cut and dried, and definitely do not establish the 600 fpe threshold as anything like a bright line. Personally, I was frustrated by the lack of any kind of confidence interval on these values. This looks more like a proposal paper than an experimental paper.

    Nevertheless, the point of this study is to show if there is a discontinuity in incapacitation effects that is attributable to the known effect of TBI due to pressure wave in addition to exsanguination. The data is compelling. There is a difference.

    Ignoring the threshold issue, there’s the simpler point: if pressure-wave effects are real (they are experimentally demonstrated in other species), then more energy released faster is more likely to result in pressure-wave induced rapid incapacitation. If the results exist, then you would expect to be able to observe them with with multivariate analysis of variance. The threshold is an artifact. The hypothesis is that pressure-wave effects overwhelm exsanguination for large experimental values of kinetic energy. I think that was demonstrated — not well enough for my book, but enough to justify further study.

    Debunking that at this point would require us to shoot our own animals. I’m budgetarily constrained, I’m afraid. Shall we devise a simpler experiment? Pressure transducers in gelatin, perhaps?

  14. Hypnagogue Says:

    Oh, missed one point:

    The distance of 12 inches was completely arbitrary — they state that they chose it due to the FBI’s Facklerite requirements. If rapid incapacitation fails, exsanguination is all that is left.

    If you focus on pressure alone and utterly ignore penetration, you can easily achieve that 1000 psi threshold with fragmenting 9mm rounds. That fragmenting+penetrating ammo (was it Precision Cartridge?) deserves a look. They may be on to something.

  15. Rivrdog Says:

    Gogue, over at my place, where I referred to this little debate, a commenter posed that the best fight-stopper might be a sawed-off M-79. He didn’t say what round to shoot in it, but in keeping with your megadeath shock theory, I presume it would be a dummy round, since explosive would be cheating and flechette wouldn’t qualify under the unitary assumption.

    Look, let go a little here: I wasn’t laughing at you and no one else was either. OF COURSE a megathunder round will hurt you worse, per shot, than a poodleshooter round. No one debates that. However, don’t belittle lethality by multiple rounds, either. When the objective is incapacitation, I don’t think you’d care if Jerry Miculek put 23 holes in your perp with a .38 Super race gun or Kristopher put one .480 Ruger hole in him with his hand cannon. If he’s dead, he’s dead. In gunfighting, I doubt that shock wave and wound cavity matters as much as does the actual time from penetration of your bullet(s) to incapacitation of the assailant.

  16. Caleb Says:

    Someday, I’ll figure out why Hypna hates my guts so much. 😀

  17. Hypnagogue Says:

    Hate is such a strong term. I prefer “wish you’d grow up.”

  18. Caleb Says:

    Why do you use your words to hurt?