The arguments based on handgun caliber mostly end up on the same mound: shot placement. The thing is that defensive pistol shots must do their job regardless of trigger press ignite predictably, get deep into vital areas to be countered by clothing and anatomy, and remain manageable to deliver follow-up shots during stress.
Gel testing today has complicated the tradeoffs. Projects constructed based on uniform protocols; short carry-length barrels, heavy-clothing barriers and the FBI penetration range of 12-18 inches; exhibit tropology that is already apparent to many instructors on the range: certain handgun calibers cause avoidable issues.
1. .22 Long Rifle
The reason why 22 LR is still appealing is that it is a soft-shooting, easy to practice and in a common place. On the defensive, the issue begins with ignition. Being a rimfire cartridge, it has a higher misfire rate than centerfire ammo, and this is not merely a theoretical difference when the firearm is used on a daily basis with the fire being infrequently fired. .22 LR also exist on thin margins, terminally. After heavy clothing, many loads do not penetrate as deeply as defensive handgun rounds are supposed to penetrate. Inconsistencies in penetration require that placement be faultless more frequently, and the conditions of defensive shooting are seldom flawless.
2. .25 ACP
25 ACP was developed to provide centerfire consistency in small pistols, however, it comes with extremely low muzzle energy and minimal capability to propel deep and also expand. Practically, it compromises the meaningful performance with a reliability increase still enforced by the current micro-compacts in larger calibers. In brief: it is not impossible to run, but there is little room to make a mistake.
3. .32 ACP
32 ACP is in a very uncomfortable sort of no-man’s land, frequently easier to fire than snappy micro .380s, and still capable of shallow performance, with load and barrel length, on its own. Barrel length does count, however, and one experiment between a 2.7-inch pocket pistol and a 3.75-inch pistol found that the extra barrel length meant a significant difference in the outcome of the tests, and that the point of interest is that it can work pretty well, despite its size, as long as you pick the ammo which will do the job. The point is that variability. A caliber that is highly reliant on a small range of loads and barrel length is not as forgiving as an average concealed carrier requires.
4. .410 Shotshell in Handguns
.410 handguns have shotgun-like dispersion, however, with short barrels the velocity decreases, and the practical performance margin becomes narrower. Birdshot rounds typically only penetrate enough to be of no use as a main defense solution, and heavier ammunition would need greater accuracy than the advertising suggests. The platform has a potential that can work, but is not always providing the outcome of a point-and-solve, as many buyers think they receive.
5. .380 ACP (with the wrong loads)
Carrying 380 is not a problem, but it is load sensitive, particularly with short barrels. Gel test procedures which emphasize heavy clothes over and over again reveal the recurrent quandary of caliber: respectable expansion that is short of it, or unproblematic depth with slight expansion. That renders the issue of .380 a caliber issue compared to a selection dilemma. In the case of casual or limited ammunition selection, performance becomes erratic within a short time.
6. 10mm Auto
The 10mm is powerful, penetrative, and has a large performance envelope. The disadvantage is that the envelope contains a lot of recoil and blast which may slow down the split times and compromise the precision of many shooters. In defensive pistol handling, controllability is frequently the key to how a shooter can provide multiple hits and they be accurate, and 10mm can be far more difficult and far more gun to achieve. It also brings more questions of pass-through risk than mainstream service calibers in built environments.
7. 38 Special out of ultra-short barrels.
38 Special is the service revolver that has earned its reputation but with short barrels the math works differently. Velocity shifts changed penetration and expansion behaviour, and were observed to have variable expansion behaviour through fabric, in gel projects that specifically compared 2 inch and 4.2 inch revolvers. That is not to say snub-nose revolvers are useless, just that they are ammunition-sensitive, recoil-shy and not as tolerant as their past implies.
8. .44 Magnum
44 Magnum has been designed with deep penetration and high energy thus this is precisely what makes it trouble in a typical defensive environment. The recoil can reduce the speed of follow-ups, and the fact that the cartridge can propel through tissue and obstacles will raise the possibility of misses, or even pass-through shots being launched with more range than the intended distance. It is a specialized instrument which requires specialized context.
In these calibers, the repeated engineering issue is not lethality. It is consistency: dependability in ignition, repeatability in penetration through clothing and manageability of realistic carry guns.Gel testing supports one ugly truth, too, which is that in heavy-clothing regimens, where barrels are short, the performance difference across loads can be the important aspect of the procedure. The caliber and the particular load act in a predictable manner, which makes defensive carry safe and more repeatable.
