As anyone that has ever shot a jug of water with a high-power handgun will tell you, yes. They absolutely do. A more appropriate question is, ‘Does it matter?‘ The answer to that is complicated and more than a little ambiguous.

Now, just so we all know where I am coming from I’m a layman. I’m not a forensic scientist, a trauma surgeon or a medical researcher of any kind. I have made no scientific study of wounds or terminal ballistics. I’ve read a lot, and seen a lot, and am basing my opinion on that. It’s arguably an informed opinion, but it’s no more than that, so take it for what it’s worth and if you’re curious do your own research.

Watching a water bottle explode or high-speed footage of the temporary cavity produced by a high-power pistol bullet is impressive. These are consistent media that respond in a consistent fashion, and can be informative. It is accepted, both in the medical community and gun communities, that bullets travelling over 2200 fps. can create a temporary cavity that exceeds the elastic limits of human tissue, and actually cause permanent damage in tissue that the bullet never actually touches (technically this is Hydraulic shock.) They also reliably create hydrostatic (neural) shock. But after thirty years of study the FBI has determined that this effect either does not occur with standard pistol bullets, or does not do so reliably enough to to be counted when evaluating the potential performance of a pistol bullet.

The thing is that unlike water or ballistic gel, a human body is very much not a consistent media. It’s full of tissues and organs of varying density and elasticity that each respond individually to shock. Some of these organs are full of in-compressible fluids, some have air in them, which changes how they respond to compression. Then there’s bone, which is a whole ‘nuther story. Regardless the FBI has decided that only the permanent wound cavity is a reliable predictor of a bullet’s potential effectiveness.

A survey of the medical literature shows that nerve damage can and does occur at a distance from the bullet’s permanent wound track even with pistol bullets, and it is very likely that the size of the temporary cavity has an affect on this. Small diameter, low velocity bullets that do not expand (.22, .25 & .32) are unlikely to produce this effect. Larger diameter bullets and higher-velocity bullets are more likely to, especially if they expand significantly. This damage is usually mild and often, but not always, temporary. Whether or not this affects whether a person is ‘stopped’ has not been evaluated, but as stated before the FBI has determined that this is not a reliable predictor of a bullets effectiveness.

There are a lot of variables; the exact bullet placement, the individual’s body type. health, weight, body fat, mental preparedness… all of these things and many more come into play.

So in answer to the question ‘Does it matter?’ the answers are, ‘Yes, unless it doesn’t’ and ‘Maybe sometimes.’ Not a very satisfactory resolution, but it’s an honest one, and it’s the one supported by the available data.

On the balance, speaking of defensive handguns, if given a choice between a high-velocity hollow-point with adequate penetration and a bullet that doesn’t expand and/or is low velocity, it would seem prudent to go with the former. The advice to carry the most potent handgun you shoot well and can carry comfortably seems to be well-advised. If hydrostatic shock is going to be a factor, the available information seems to indicate that it will most likely occur with a powerful cartridge, and an expanding bullet will enhance this effect. Probably.

As a caveat, with handguns the most important and reliable predictors of effectiveness are still, in order, Penetration, Shot Placement and Permanent Wound Cavity… but it doesn’t hurt to stack the deck. If you can achieve those three things, adding a large temporary wound cavity certainly isn’t going to make it less effective! In a defensive shooting any advantage is worthwhile, as long as it doesn’t degrade the three factors listed above.

Micahel Tinker Pearce, 1 September 2020

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