Defensive handgun performance is not about swagger but rather about engineering: you must have a reliable ignition, sufficient penetration to hit vital areas, and recoil that will still allow accurate hits to be made when fine motor control is lost.
Caliber arguments omit another aspect, ballastic gelatin and barrier testing. Clothing may fill a hollow point, wallboard may make a projectile intended to shoot deep turn into a deep-penetrating punch, and short barrels may rob a stack of bullets of the velocity which it requires to act as it is advertised to act.
Such calibers and setups have the tendency to disintegrate under the pressure since they cannot efficiently function in thin margins.
1. .22 Long Rifle
The largest defensive issue with 22 LR is not some mystery, but design. Rimfire priming is less consistent inherently than is centerfire and a defensive pistol is no place to find out about a dud. Around the time a round is fired, short handgun barrels may still leave.22 LR left hanging on the fringes of the velocity required to cause any meaningful penetration and any hope of consistent bullet performance.
It is barrel length swings that are significant when you have already thinned the baseline, and published comparisons have found that short test barrels have 126 fps more velocity than the longer test barrel. Such a dissemination may be the distinction between just sufficient and not sufficient.
2. .25 ACP
25 ACP also solved an ancient pocket-pistol dilemma with an extremely small centerfire cartridge, though not the physics dilemma. It usually requires little power and has little penetration, and it tends to appear in pistols with small grips and unsophisticated sights that cannot be reasonably accurate as some may wish to think.
The defensive “margin” of the caliber is narrow in terms of its performance. In a case where circumstances are not in favor – angles, clothing, imperfect hits – there is less space in which the cartridge can recover.
3. .32 ACP
32 ACP may be an improvement over .22 and .25, yet it exists in the realm where expansion and penetration becomes load and scenario specific. Clothing is a recurring delinquent in this category: hollow points in this category can either plug, fail to expand, or have inconsistent behaviour upon going through fabric.
Platform selection may also undermine the principal strength of the caliber. The extremely small (under 32) and lightweight pistols are hard to hold, and they may not cycle as reliably even at speed, and it eliminates the soft recoil that made the cartridge attractive to shooters to begin with.
4. .410 Shotshell Out of Handguns
The marketing argument is easy gunpow blast effect of the handgun-sized package- but short barrels penalize shotshell performance. Velocity is diminished, patterns are opened quickly and small shot may not have enough penetration to consistently reach vital organs, particularly when the target is on an angle or wearing clothing.
Platform-sensitive also can be slug-type .410 defensive loads. Hornady had problems in testing with the slug of its .410 Critical Defense; it tumbled, which rendered its behavior in the air more difficult to predict at range.
5. .380 ACP From Micro Pistols (Ammo-Sensitive Setups)
380 ACP is working, but it makes a juggling act at the shortest barrels. There are loads which swell and break. Others steal in and do not do much. When heavy clothing is introduced into that trade off, it becomes even more acute as it makes marginal expansion nonexistent.
Huge gel projects with huge clothes have repeatedly discovered that .380 was one of the most feeble mainstream defensive choices to provide consistent, well-balanced outcomes in working with numerous loads. It is not power per se that is the problem of the cartridge; it is regularity in little guns where speed and bullet design are on borrowed time.
6. 10mm Auto (Full-Power Loads in Carry-Sized Guns)
10mm Auto provides honest horsepower- 600ft-lbs or more frequently- with recoil and blast that can decelerate follow-up strikes. The time and accuracy afforded in a defensive situation are not indulgent, and the cartridge can convert an issue of shooting into an issue of recoil management.
Deep penetration may also prove to be a liability as it may happen when a bullet is missed or penetrated. The cartridge can be clearly designed to permit penetration in a single lane, and beyond that, the tradeoffs build up rapidly.
7. .38 Special From Ultra-Short Barrels
38 Special has made its popularity in service-length revolvers, but the snub-nose format alters the arithmetic. Short barrels lose velocity and most hollow points require that velocity to continue to expand particularly when they come out of clothing. Expansion failure results in a solid acting .38 that drives deep without providing the desired wound mechanics.
Checking in 2-inch and 4.2-inch revolver barrels shows the extent to which performance changes with barrel length and how jacket can readily spoil the expansion of certain loads.
8. .44 Magnum (Defensive Use Tradeoffs)
44 Magnum is a headliner and much of the time 1,000+ ft-lbs and recoil measures the same. Such a mix can slow down the correct follow-up shots and hasten and repeat hits more difficult than they should be. Carry and clean deployment is also a challenge to platform size which is significant when time is compressed and movement becomes cumbersome.
Practically in defensive shooting, the caliber will tend to compel the shooter to spend time and control to purchase ballistic capability that cannot be effectively utilized in a stressful situation.
It is not the trend that these cartridges are incapable of being dangerous. The tendency is that they require narrow conditions- ideal reliability, ideal loads, ideal barrels, ideal angles, to act predictably.
Barrier work explains the importance of consistency: holes may fill up on clothing, and wall material may weaken expansion and alter penetration. Modern baseline is still the 12-18 inches of penetration target that is usually employed in standardized testing since defensive shootings do not typically provide ideal angles, hits, or clear corridors.
