In recent decades 9 x19mm has come to dominate other calibers for civilian, police and military handguns, and it’s fair to ask why? What has caused this? Some maintain it’s a bureaucratic decision made by bean-counters with a depraved indifference to the lives and safety of troops and officers (we call these people idiots. It’s a technical term.) But it really, really isn’t just bean counters and bureaucrats. It’s a practical decision firmly based in reality.

Famously during the Philippine Insurrection the US Army’s .38s failed to stop the enemy. So did British pistols and .30-40 Krag and .303-caliber rifles. In a desperate move the Army pulled .45-caliber revolvers out of storage and began to issue those, but the conflict ended before meaningful numbers of these guns re-entered service and no useful data was generated. Modern gun mythology is that the .45s stopped the baddies cold, but I have been unable to come up with any substantive evidence of this or even that these weapons were widely distributed before things wrapped up.

As it turns out one of the reason it was so hard to stop these attackers was that they were Committed Attackers, suicidely determined to take as many enemies with them as possible. They were also drugged to the gills. Subsequent experience has shown that absent a hit that causes catastrophic damage to the central nervous system such people are very difficult to stop with any handgun of any caliber.

Subsequently when the Army was looking to adopt a new, modern service pistol the Thompson-La Garde study was undertaken. This used a variety of means to determine the potential stopping power of proposed service calibers using a variety of mechanisms including momentum transferred to the target. This resulted in the recommendation that the army adopt a weapon of .45-caliber with a 200gr. bullet with specific characteristics, and given the technology of the time and the thinking involved this was not an unreasonable conclusion. Many gun enthusiasts are aware of this without knowing the specifics of the study, and they miss or gloss over one of the central conclusions of the study: Hit location is of critical imp0ortance.

Their conclusion was that if you are going to put a service pistol in the hands of people with minimal training you cannot assure good marksmanship, so one should arm them with what seemed to be most effective cartridge and bullet absent that quality. Not at all unsound reasoning.

Then as Othias is fond of saying, ‘War were declared.’ In WW1 pistols of calibers ranging from .32 ACP to .455 were widely deployed and after-action analysis reached a startling conclusion: Militarily speaking the effect of pistols was negligible to virtually non-existent regardless of caliber.

In the interwar period most European powers adopted the 9mm Parabellum, and there is little evidence that they found this caliber wanting in actual battle in WW2. After the war 9mm became the most widely adopted military handgun cartridge in the West and became the NATO standard round. The US resisted changing for decades, not because of any inherent belief in the superiority of .45 ACP however. It was because we had millions of leftover 1911A1s and enormous stockpiles of .45 ACP ammo left over. Changing to a new service pistol and caliber would be expensive and given the increasingly unwieldy and corrupt procurement practices it was going to be a huge pain in the ass for something that was of comparatively little military significance.

Meanwhile on the civilian side a combination of anecdotal evidence and resulting hype in gun media combined with a cult of personality or two and caused the .45 ACP to be touted as the only worthy defensive cartridge. Period. Efforts were made, not to determine if this was true but rather to support this conclusion, and any evidence that did not support this conclusion was disregarded. This is not at all to say that .45 ACP is not a good, effective cartridge. It was and still is.

But time marches on and fashion changes. The broad introduction of high-quality, reliable high-capacity 9mm pistols in the US in the 1980s started a sea-change in the caliber debate. A number of famous police shooting incidents caused renewed study of the relative effectiveness of service calibers, resulting in the adoption of 10mm. But this was determined to be problematic as a general-issue cartridge and the .40 S&W was widely adopted. It was The New Hotness and the best thing since sliced bread.

Except it wasn’t, actually. It was in fact a perfectly good cartridge, but it was the answer to the wrong question. Long-term studies by the FBI and others revealed that, wait for it…

… Hit location is of critical importance.

Analysis of actual shootings also revealed that within limits caliber was of less importance than previously believed. There was in fact of no quantifiable difference in effectiveness between service calibers in real-world shootings. A bullet needed to penetrate deeply enough to disrupt critical structures in the human body, and it needed to hit those structures. Oh, and a larger permanent wound cavity was better than a smaller one.

The conclusion that this third factor meant bigger bullets should used was rapidly pounced upon by large-caliber advocates, but in fact to some degree bigger bullets don’t produce bigger permanent wound cavities because human tissue is elastic. It stretches and rebounds. A .45 caliber bullet does not normally leave a notably larger permanent wound cavity.

OK, stop for a minute. I think it is very likely that in absolute terms some calibers are objectively better with all things being equal. But in a gunfight all things are never equal. There are simply too many variables to concretely quantify this based on real-life shootings.

What bigger bullets indisputably do produce is more recoil. Most people that are issued a duty weapon are best termed casual shooters. On average they qualify a time or two a year and practice very little. Recoil is an issue for a number of reasons, mainly that it makes it hard for casual shooters to reliably get good hits with rapid follow up shots. This matters in a gunfight because you need to hit those important bits in the human body and in the chaos of the moment more chances to do so is better. Which brings us to capacity. If more hits are better it’s good to have more bullets to make those hits.

You simply cannot put as many .40 or .45 caliber bullets in a service handgun as you can 9mm, especially not if that gun is going to be manageable for people of all shapes and sizes. Because reality.

9mm is the most common service caliber in the world and is immensely popular with the civilian market, so ammo is comparatively inexpensive. It is easier to train casual shooters to employ it to a minimum standard of effectiveness. It is effective enough and the guns hold more shots. These all make it not necessarily the best possible defensive pistol cartridge but arguably the best compromise for an issue weapon and as such it has been almost universally adopted for that use. By and large it has proven as good as anything in that role. The reasons for military, Law Enforcement and civilians all standardizing on the 9mm are based in reality and pragmatism, though elements of fashion are definitely involved.

There’s pushback, of course. I mean, have you met people? There are still die-hards that insist .45 ACP, 10mm or whatever is the best, ultimate and only worthy choice, and you are a moron if you think otherwise. Fewer than there used to be, but they are definitely still making themselves known. See the earlier reference to ‘idiots.’ By and large we can ignore them.

OK, it makes sense as a service cartridge but what about us civilians? Is 9mm the best choice for us? Maybe, maybe not. Depends on the individual. Certainly from a logistical standpoint it’s a good choice; availability, cost and load development are all very much in it’s favor and you certainly won’t be starved for practical, high-quality handguns for almost any self-defense need and most budgets.

But in the end your best choice is not caliber, bullet design or logistical issues. It’s you. Hit location is of paramount importance, and training is the best way to insure effectiveness.

Stay safe and take care,

Michael Tinker Pearce, 11 September 2023