The debates on the defensive caliber level can easily be reduced to slogans, yet the trick of it is mechanical: reliability, decent penetration, and manageable recoil must appear simultaneously, under pressure.
That fact is the reason why some cartridges and even how people are traditionally using them continue to be discussed in the after-action evaluations and ballistic tests as weak links. The successive rounds that follow are not useless, but they keep on prodding compromises, which play when accuracy and repeatability becomes the entire game.
1. .22 Long Rifle (as a carrying round)
A 22 LR is universal as it is now simple to shoot and simple to practice. The defensive engineering flaw is the rimfire ignition system, which is more prone to misfire than centerfires- an intolerable failure mode when there is no time to trouble shoot a click as opposed to a bang. Even at full speed, handgun velocities do not give much room to standardize in clothing and at non-optimal angles.
Gel data may be good enough on a lucky day, but decision-making of duty grade is about repeatability. Weak hits which do not strike essential buildings leave the shooter to volume and position, and that is what stress destroys initially.
2. .25 (legacy pocket-gun caliber) ACP
25 ACP was meant to make small pistols centerfire-reliable, but recent experimentation and practical results continue to demonstrate what its low case capacity is purchasing: extremely low momentum and minimal tissue disturbance. The round often cannot achieve the depth of calibrated gel when it is used with low muzzle energy (typically less than 70 ft-lbs) used.
It has platform reality as its other issue. Most ACP .25 pistols are old models which have small sights and short grips that complicate rather than simplify rapid and responsible shooting, even though the recoil is no more than mild. The better than nothing niche which the cartridge has held historic status has been squeezed by the modern stronger micro-9 and micro.380.
3. .32 ACP (easy recoil, indiscreet terminal results)
The reason why 32 ACP is a loyal brand is that it is easy to shoot and it is usually available in slim pistol formats. Its shortcoming is that comfort does not ensure adequate penetration, particularly of swelling bullets which can block or fail to penetrate when discharged through short barrels. That makes the decision between non-expanding loads that potentially act like drills, or hollow points that potentially do not drive deep enough.
Availability makes it even more complicated, as well as the age of the platform. Most often-used .32s are older models and even where there are modern firearms the choice of ammunition is thin relative to mainstream service calibers- making it less likely to find an ammunition load that works reliably and with consistent performance.
4. .410 revolver (shot)
Hybrids Revolver-shotguns are a marketing of a very basic concept: point-shoot with a sloppy pattern. Theoretically, shallow rifling and short barrels can give a pattern that opens quickly, leaving gaps in them big enough to miss small targets at common room range. The spreading of that will also be a liability and push the pellets out of the target line.
Load-dependent, performance lightweight birdshot typically does not penetrate anything meaningful, and buckshot loads are only useful within a small envelope. The system also introduces tradeoffs of bulk and handling that do not necessarily translate to improved hit probability, which is the determining measure.
5. .380 ACP loads not penetrating to minimum
380 ACP is at a slender benchmark of performance where design of bullets is of more importance than marketing. Popular hollow points swell rapidly and come to a halt, particularly of short barrels like those of pocket pistols. Other loads penetrate, but act as little non-expanders, restricting the diameter of permanent wound path.
In the case of carrying .380, the engineering objective is not peak expansion, but a balanced load, which is capable of reaching the structures of interest. At that, the shooter is left with a cartridge that is nice to hold but intolerant to imperfect angles and walls.
6. 10mm Auto (power that chastises consistency)
10mm Auto has the horsepower it may well be over 600 ft-lbs in full-strength loads and it is capable of deep driving. Defense issue The most frequent one is the recoil and blast decreases the velocity and accuracy of follow-up shots in numerous shooters, which occurs primarily in small handguns. It is not a weakness of character; it is merely physics manifesting itself in the hands.
It also makes the occurrence of undesirable barrier travel of built environments more probable. In one interior-wall experiment, Handgun rounds (9mm and .45 ACP) all went through at least six sheetrock-walls and in 10mm case, more than 10 walls. There is no free power; it transforms what nothing can do.
7. .38 Special ultra-short barrel (the snub-nose penalty)
38 Special has an extensive record, though short barrels below two inches bleed velocity, and velocity is what most hollow points require to open and continue penetrating. What this has produced is a cartridge which can appear beautiful on paper, and dismal in gel, when discharged through the smallest revolvers particularly when loaded inside clothing where crevices and bullets act as solid particles.
+P pressure may induce recoil without ensuring an improved terminal outcome in such platforms. There is no sure way but the loading of loads that was designed to fit into short barrels and the acceptance of the fact that the smallest revolver require more ability per shot, rather than less.
In these instances, we do not find the theme of caliber snobbery. It is the design limits of engineering ignition, barrel length, bullet design windows, recoil impulse and how ordinary building materials cannot stop projectiles.
In defensive shooting, results are followed by the capability to make repeatable hits which penetrate sufficiently. Any cartridge which diminishes reliability, narrows performance margins, or slows a follow-up shot, has to multiply stress at the very time the system can least afford it.
