The reason why small handguns are a solution to a real problem is because on the one hand it does get carried. The engineering drain is that the same small barrels and small cartridges that make a pistol easy to carry about will also make terminal performance excruciatingly inexcusable particularly where clothing, bone, or immoderate angles are concerned.
This is why pointless arguments continue to revolve around a stultifying figure 12 to 18 inches of ballistic gelatin penetration. Not a machismo norm, but a geometry norm. In case of a threatened blade, movement, or partial protection of the by an arm, the bullet may have to travel more than “half a chest” to get to a target which will consistently shut down the body. The FBI range is there to accommodate that ugly truth, and contemporary testing is inclined to regard it as the standard of cartridges that are destined to be used in defense.
The problem is manifested in hard measurements by the pocket-class cartridges at the lower end of the power spectrum. In a Beretta 950, with a 2.4-inch barrel, a.25 ACP defensive loads had a landing range of about 10 to 11 inches in gel and were indicated to have virtually no expansion, compared to a set of tests where Speer Gold Dot stopped at about 10 inches and Hornady Critical Defense at about 11 inches, both short of the mark. It is criticism of the caliber that has been relentless and can be summed up by the statement of Lt. Col. Jeff Cooper: “Carry a .25 if it makes you feel better, but never load it. If you load it, you may shoot somebody, and they may become angry and do you a serious jury.” It is precisely that lack of portability and performance that makes the.25 ACP such a difficult sell when there are other options.
Another variable is ignition, with rimfire being more consistent than centerfire: Rimfire cartridges can be precise and fast to shoot, but the priming is less consistent. Barrel length is also variable in performance. In a series using two handgun barrels, one of the .22 LR configurations had an average increase of 126 fps of velocity between a 1.9-inch revolver and a 4.4-inch pistol but did not necessarily penetrate best when the faster loads were used. Although seemingly “defense-oriented”, even the offerings of .22 LR may act as penetration-only tools: one test of Federal Punch 22LR Personal Defense revealed no expansion with various pistols, and penetration of around 10 inches to as much as the high teens, depending on the gun.
380 ACP is on the fringe where the prudent design of loads is more important than the caliber anthropology. Neither can short barrels take away sufficient velocity to render hollow points spotty after thick clothing, nor a slight variation in barrel length can be the difference between opening fire and closing like ball. A single study observed that extremely minor variations in barrel length of the 2.5-3 inch range can significantly alter the velocity and the bullet action. The “just run FMJ for penetration” argument is also where such problems come in: FMJ can feed well and penetrate, but in many cases it substitutes a large wound channel with a through-and-through effect that will not always bring a fight to an early close.
Another case of packaging creating compromises is the .410-from-a-handgun concept. Performance may be acceptable with some .410 buckshot penetrating at respectable depths in bare media, though when barriers are introduced, the performance can decline dramatically, and patterns and pellet energy change by load and platform radically. The performance of tests fired at a .410 shotgun has revealed that water-penetration on some loads of buckshot is good, but there is no certainty that the action will be repeated with short, rifled revolver barrels where the patterns open, and the projectiles may act differently. That is, “multiples projectiles” does not warrant the type of deep, consistent course, on which defensive requirements are founded.
The adoption can make or break even where a cartridge has been designed to be like a tested one. The .45 GAP was intended to have a shorter case and a higher pressure ceiling, to replicate the behavior of .45 ACP, although it could never create the ecosystem that makes a defensive caliber workable over decades. Having few pistol and load variants, it was a technical fix seeking a permanent issue.
It is not that small cartridges are safe. It is, that defensive ballistics is a matter of margins and that the smallest rounds are those with the least margin; to penetration, to expansion, and in some cases to reliability in ignition. When space is measured in inches the engineering limits of miniature platforms become apparent in a short period of time.
