The line, “Any caliber works with perfect shot placement” has been able to outlive itself because it has an element of truth. The mechanical issue is that defensive shootings are not usually going to provide the perfect, and the cartridge must bear the remainder of the load. Current defense analysis continues to revert to a single reproducible standard one penetration sufficient to get to essential tissue following typical impediments. Most trainers and testers compare that to the 12-18 inches of ballistic gelatin standard quite commonly talked about in the duty-ammo selection.
Loads which can hardly get to that window, or which get to it only sporadically, present less space to real-life variables such as heavy clothing, angled shots, or intermediate bone. All the cartridges listed below have a role in the history of firearms or recreational shooting. The problem is defensive carry, in which the adequate is sometimes an engineering failure mode, and not a personality feature.
1. .22 Short
The.22 Short is a low-recoil, low-report cartridge that has a long history in the history of American rimfire. It can be fired at will in small pistols and controlled with ease and as such is an appealing choice since it is a better than nothing choice.
On the defensive, it is a physical constraint. The light bullet and small powder capacity of the cartridge limit velocity and that is revealed where it counts: penetration and uniform disorientation of vital structures. The .22 Short is not reliable in reach when obstacles come into play, such as thick clothing, arms in front of the torso, and oblique angles.
2. .25 ACP
25 ACP was designed to address one particular issue: create a pocket pistol cartridge, which lights off more predictably than rimfire in very small arms. That centerfire primer benefit is genuine and in good pistols the cartridge can be cycled without issue.
There is a defensive gap between reliability of ignition and reliable terminal performance. In gel work on pocket calibers, loads of.25 ACP did not tend to go beyond significant penetration limits and even those which did penetrate well did so inconsistently. In a defensive scenario, that transforms minor differences in angle, clothing or target anatomy into huge variations in outcome.
3. .32 S&W (Original)
The prototype .32 Smith and Wesson is of a period of pocket-sized pistols and reasonable hopes. It is mild spouting and mechanical pleasant in old and traditional guns.
In the modern performance comparisons within the family of.32, it is evident why it has been overshadowed. Subsequent cartridges all called .32 S&W Long, .32 H&R Magnum, and .327 Federal Magnum have higher performance ceilings and provide greater velocity and enhanced opportunities of satisfactory penetration over a broader range of loads. The original.32 S&W does not have that headroom, which is important when there is inaccurate placement of the shot, or when the projectile has to penetrate intermediate media.
4. .410 Bore from a Handgun
The concept of the .410 revolver sells: It has several projectiles, a big muzzle, and gives you the feeling of shotgun dominance in a sidearm. Practically the payload acts in a manner not expected by many people due to short barrels and rifling restrictions.
Birdshot is a steady weak point of defensive application. Birdshot penetration even in shotgun tests can be shallow in liquid and other media which reflects long-term worries regarding stopping a determined attacker. Buckshot and specialty are capable of being better, although these still trade pellet weight, velocity, and pattern behavior in ways that require careful consideration of what the gun actually does with at realistic distances.
5. .22 LR (Pocket-Sized Semi-Autos, in particular)
The use of 22 LR has its advantages: it is low in recoil, high in capacity, and it is available on a wide variety of platforms. In defensive handguns, however, rimfire brings in a new profile of reliability compared to centerfire.
With rimfire priming, empty shots are more probable than with centerfire primers and the geometry of a cartridge can be less tolerant to the magazine-fed actions. Advice on testing and training is usually aimed at minimizing such problems such as ammunition of higher quality, the gun should be cleaner than usual centerfire standards, and it is also important to confirm that a particular pistol/ammo combination functions. The method of avoiding any feeding issues is by picking a revolver, a misfire can be fixed by just pressing the trigger once more.
6. .380 ACP FMJ
380 ACP is close to the bottom of the range of widely accepted cartridges of defense, and is made or broken by load selection. Full metal jacket has been widely used because of consistency in feeding and due to the hope of penetrating deeper.
The wound tradeoff is wound mechanics. FMJ may act as a slender punch in soft tissue, and based on the target anatomy and speed, may fail to reach the target that needs to be reached or may pass through with minimal disturbance. In comparison, current defensive loads of.380 are designed to achieve a balance between penetration and expansion, but the energy budget available to the cartridge is very limited, resulting in some loads being at the limit of that balance, and some being below it.
7. .45 GAP
45 GAP is a technical way of solving a packaging issue: provide a shorter cartridge with the performance of a .45-caliber round, but with a smaller grip that can fit into a smaller pistol. The shorter case and the total length are compared dimensionally, with the overall length of similar bullet weights and diameter to those of the.45 ACP being maintained.
The penalty of engineering rather than ballistics is ecosystem. In order to approximate .45 ACP performance in a smaller envelope, it was necessary to design.45 GAP to have higher maximum pressure than normal .45 ACP. However the cartridge never achieved wide followings and modern shooters have poor platform and load support relative to the strong bench and long life cycle of .45 ACP. A niche cartridge decreases resilience in the context of defensive planning in terms of training, obtaining compatible loads, and the long-term support.
The choice of defensive caliber usually comes out as a discussion on what stopping power is, yet the more realistic question is more basic: how much uncertainty a cartridge can take and still achieve the minimum performance requirements. Carridge that regularly have difficulty in penetrating, maintaining its consistency when using clothing or offering long term support limits the error margin. In a position where the effects are short lived, that margin is the entire game.
