…it’s complicated, because sometimes bigger isn’t really as ‘bigger’ as you might think.

Proponents of the larger calibers point out that a bigger hole does more damage. A bigger hole also means blood pressure drops faster. Seems like a no-brainer, right? But the collected data from actual gunfights doesn’t support this conclusion.

Research in recent years has shown little significant difference in the real-world performance of different calibers between .380 ACP all the way through .44 Magnum when multiple shots are fired. Service calibers (.38 Special, 9x19mm, .357 magnum, .40 S&W, 10mm and .45 ACP) actually perform surprisingly similar shot-for-shot too.. This is baffling; there’s a lot of variation there.

Here’s an experiment that may help explain this: get a thick piece of rubber and shoot it with a .380 ACP and a .45 ACP then look at the holes. The difference between the holes isn’t obvious. That’s because the material is elastic and stretches around the bullet as it passes through, then snaps back. The trick is that human flesh is also elastic and tends to do the same thing.

Regardless of the specific cartridge we’re looking at bullets between .355″ and .451″ in diameter. The difference is 1/10″. That’s not much, and as it turns out it’s not enough to overcome the elasticity of human flesh. Coroners and emergency-room personnel report that they often cannot tell what caliber produced a gunshot wound from a handgun until or unless they find the actual bullet that produced it. This is because flesh is elastic. We’re stretchy.

In other words the ‘hole,’ called the Permanent Wound Cavity, of a .45 ACP isn’t actually significantly larger than the one produced by the .380.

Surprisingly hollow-points don’t change the equation as much as you might expect. Modern hollow-points expand quite a bit, and if you’re relying on blood-loss to stop an attacker the extra damage of a large-bore expanded hollow-point is likely to speed things up slightly. Maybe not enough to make a difference though; an attacker that still has time to kill you isn’t ‘stopped’ in any meaningful sense. Neural Shock from shockwaves transmitted through the body may or may not have an effect, but this seems to be unreliable at best as a stopping mechanism.

The simple truth is that the way you stop an attacker with a handgun (quickly enough to do you any good) is to hit the central nervous system or major elements of the circulatory system, specifically the heart and major arteries. Any bullet that penetrates deeply enough to break the things you need to break can do the job. Any bullet that doesn’t hit these things relies on other methods like gross physical damage to non-vital structures, which is generally a pretty slow way to stop an attacker. In those cases a larger expanding hollow-point bullet is likely to do at least a slightly better job, but that might not be enough to make up for slower follow-up shots.

This may in part be because there are two kinds of ‘stops;’ the Soft Stop and Hard Stop. A Soft Stop (often called a Psychological Stop) occurs when the person consciously or unconsciously, simply gives up or runs away. A Hard Stop (called a Physiological Stop) occurs when an attacker is physically incapable of continuing their attack. A hit in the hand from a .25 Auto can produce a Soft Stop. A hit from a .44 magnum that misses everything immediately relevant can’t produce a Hard Stop. The only way either caliber produces a Hard Stop is to hit the central nervous system, which either caliber can do, or cause catastrophic damage to the circulatory system. An expanded .44 magnum JHP is a lot more likely to cause the latter than a .25 ACP, but .25 isn’t really part of this discussion.

Any bullet that hits the CNS or major elements of the cardio-vascular system is likely to stop someone pretty quickly. In the chaos of a gunfight you are shooting at a relatively small target that you can’t necessarily even see; more chances to hit those targets might be a good idea. Also if the situation is bad enough that you legitimately need to shoot someone you need them to stop as quickly as possible, so being able to put repeated hits on the target as quickly as you can manage is important.

This is why the FBI went back to 9x19mm. It has enough penetration, and recoil is light enough that the average agent can learn to put multiple hits on target fast. On the balance they feel it works better for their needs than a more potent caliber, even if it could be demonstrated that round was significantly more effective. Which, based on the data available, it can’t.

Then there are the variables. The attacker’s physiology; large small, skinny, heavy, fat; these things all make a difference. As does the attacker’s psychology and mental state. How committed are they? What is their goal? An attacker that wants your wallet is going to be a lot easier to achieve a Soft Stop on than one that is absolutely determined to take you down with them. While we’re at it let’s talk about chemicals; are they drunk? Stoned? How much and on what? Is an attacker likely to be in light clothing or bundled up like an Arctic explorer? There’s also movement, environment, barriers, innocent bystanders… the list goes on and on.

So we can all just pack a pocket .380 and call it good? Probably not. For a person living in an urban environment where the principle threat is a full-frontal confrontation with a mugger or perhaps a car-jacking attempt that might well do fine. But someone living in a rural area that might encounter hostile wildlife might reasonably think a 10mm is better suited to their needs. In an apartment building over-penetration is a serious consideration; in a sprawling suburban neighborhood rather less so and in rural environments it could be a non-issue.

I’ve also talked before about the difference between police use of deadly force and civilian needs. The civilian is much less likely to encounter a committed attacker, less likely to need to penetrate barricades or engage in a protracted fight, less likely to have to fight at any significant range and is more likely to have the option of disengaging if circumstances allow. Caliber and weapon selection is different for civilians based on the most likely threats, and there’s a balance each of us has to find based on our individual lives, skills and circumstances.

All this being said ammo selection is not irrelevant; whatever caliber you choose modern, proven defensive ammunition should be employed in whatever caliber you select. Maybe it’s just stacking the odds in your favor, but that’s definitely worth doing when lives are on the line.

I think it is possible that some calibers are somewhat more effective than others, but with all the variables involved, real-life shootings seem to indicate that difference between calibers alone is not decisive. Consider your own physique, skills, abilities, style of dress and circumstances and choose based on that rather than some dubious thought that a given caliber is a better ‘stopper.’

Michael Tinker Pearce, 26 May 2021

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