We do not have any magic handgun cartridge, just tradeoffs that become apparent quickly when stress sets in. The contemporary terms of the debate have changed to not so much knockdown power but to quantifiable performance: reliable ignition, sufficient penetration to critical targets, manageable recoil to make follow-up shots, and bullets that will work reliably behind clothing and other everyday obstacles.
That change is important since most of the popular carry decisions continue to be rooted in a reputation, nostalgia, or convenience. The same poor areas have been demonstrated with the cartridges below in training room, ballistic-gel workups, and face-to-face discussions about real world performances, again, in comparison with the better-engineered defensive loads today.
1. .22 Long Rifle (Rimfire)
The popularity of 22 LR is due to low recoil and the ability of pistols to be small, however, the ignition type is structurally less reliable than centerfire. Premium .22 will work but misfires are common enough to be significant in a defensive tool, the main article quotes 127% in premium loads and up to 810%with bulk ammunition. Terminal performance is also not even: most loads of.22 have a hard time breaking through 1218 inches of ballistic gelatin commonly used to measure when critical anatomy is reached. Specialized loads are capable of enhancing results however the platform remains a reliability and penetration gamble when compared to mainstream centerfire offerings.
2. .25 ACP
25 ACP was intended to replicate the performance of the .22-class in a centerfire, although in practice it has very low energy and a poor wounding capability. In the primary article, it is observed that most loads give less than 70 ft-lbs, and expansion is frequently non-existent, and penetration often less than modern. One of the most widely quoted field-data in the discussion of defensive shooting is a compilation by Greg Ellifritz, in which 35% of those who fired with .25 ACP had not incapacitated the person they shot. In electrical engineering practice, it has been superseded by the cartridge: small pistols have frequently been made to take more competent rounds and demand no corresponding terminal compromise.
3. .32 ACP
The strength of 32 AACP lies in its ability to be controllable, but its results lie too near those of rimfire-based pistols with short barrels. The primary article puts average energy at 125170 ft-lbs, and expansion and depth varies following heavy clothing. It is not that .32 can not work, it is that it often performs at the borderline, with a projectile being a little too long or a little too bulky, or a barrier material, that it is either a matter of life or death.
To shooters able to cope with a little more recoil, moving up to more familiar defensive chamberings will usually give them a richer choice of loads that have been designed to address contemporary penetration and barrier requirements.
4. .410 Shotshell Fired Revolver Fired.
Revolvers which were designed to shoot .410 shotshells with the promise of a shotgun-like pattern in a small handgun-like package, however, have short barrels and handgun ergonomics that make that promise erratic. The primary article outlines patterns to open dramatically at close range, such as spreads as close as 30 inches in 15 feet, which makes the matter of accountability evident. Even with birdshot penetration may be poor: in the demonstrations used by Tom Givens mentioned in the main article, a shot made of #9 could not penetrate a plastic bottle, and even with a shot made of #4, we could not penetrate 3/4 inch plywood. Patterns can narrow with buckshot loads at close range but the whole system is a workaround, not as predictable as more conventional handgun cartridges, intended to penetrate reliably and produce a consistent point of impact.
5. .380 ACP Round That is not Penetrating with Micro Pistols.
380 ACP is potentially viable, though it is a caliber where a selection of ammunition and barrel length is capable of eliminating the margin of safety. Some hollow points in short barrels enlarge prematurely and do not reach the desired depth of penetration so commonly desired in defensive testing, and others do penetrate and enlarge little. It is not the headstamp that is a problem, but rather the combination of small guns, steep loss of velocity and bullet forms that had not been optimized to meet micro-barrel impact velocities. This produces a cartridge that will require additional homework and additional validation than many carriers would like it to, particularly when it is compared with modern service calibers which has a richer bench of repeat performing loads.
6. 10 mm Auto (typical Urban concealed carry)
10mm Auto has a high penetration and energy, which also has its own recoil, blast, and additional over-penetration risk. The primary paper observes that with optimized 10mm loads, it may be possible to achieve the same endpoint as testing in the .40 S&W in terms of gel tests, and poses the question that is practical: does the additional cost of recoil provide any defensive value against human adversaries?
The wider literature on stopping-power also undermines the notion of bigger-better-best; even the FBI research has been summarized as indicating that the tracks left by wounds of most common handgun calibers cannot be differentiated by clinicians during surgery or autopsy, which is a notion referred to as FBI ballistic research. Realistically, repeatable hits and controllability are of more significance than headline energy figures in the majority of concealed-carry settings.
7. .38 Special out of Ultra-Short Barrels.
The defensive history of 38 Special is extensive, and ultra-short barrels rob the shot of the velocity which many hollow points require to travel dependably and expand. In sub-two inch revolvers, the author observes that most loads do not perform well on a minimum of 12 inch standard which is often used as a defensive-gel standard and that sometimes clothing can plug the hole and prevent further fire, which complicates matters when a follow-up shot is required most. +P ammunition may only increase recoil without an equivalent increase in terminal effect on such small platforms. Engineered loads designed to be narrow with short barrels can also reduce the gap, but the performance of the cartridge will now be much load-dependent than its image implies.
The overall pattern of failure (though with varying degrees of predictability) in all of these cartridges is the same: unreliable ignition, shallow penetration, unreliable expansion, or recoil that slows on follow-up shots. The physics will remain the same due to a caliber being popular, compact or historically revered. The order of priorities that have always stayed the same in the case of modern testing and old stopping-power arguments is that, first of all, there must be a reliable platform, secondly, the ammunition must have the adequate penetration, and, finally, the shooter must be able to fire several accurate rounds into vital areas when stressed. It is those factors that are more likely to count as opposed to seeking a mythical one-shot solution.
