A home-defense handgun does not have to be exotic. It must work every time, push deep enough to find something important and must remain manageable when the small muscles have broken.
It is that combination that particular calibers and configurations begin to fail. Others have ignition reliability issues, others are not able to reliably achieve accepted penetration and others provide recoil and blast that retards the only thing that counts in a fight accurate follow-up hits.
Blastastic gelatin is neither an individual nor is it a problem of consistency, but it is a yardstick. The testing system used by Lucky Gunner, which included shooting five rounds at a heavy-clothing barrier and measuring penetration and expansion, was based on the 12-18 inch penetration range of the FBI, which is a valuable point of reference in the comparison of defensive loads.
1. .22 Long Rifle
The reason why 22 LR can be found everywhere is that it is easy to shoot. The issue is that its rimfire ignition system compromises the cost with consistency and defensive application penalizes any growing percentage of misfires. .22 LR tends to be on the incorrect side of the penetration-versus-expansion tradeoff even when it is fired, particularly after clothing is involved. Practically, .22 LR can harm and even kill, yet there is not much of a margin when the target is angled or partially obscured, or even not responding in accordance with paper targets. A defensive cartridge is evaluated based on repeat performance, not optimal shot placement.
2. .25 ACP
The reason why 25 ACP exists in large numbers is that early pocket pistols had to have a small cartridge that was centerfired. Nowadays its role is largely historical. Normal energy levels are so low that the modern hollow points can do little that they are designed to, and the small pistols that can hold the energy usually offer short sight radii and few features of handling. .25 ACP as a defensive option presents the shooter with a tradeoff involving a compromised terminal performance with no significant reliability or control benefits over superior performers.
3. .32 ACP
32 ACP is still attractive in regards to soft recoil and slim firearms. The disadvantage is that the caliber often becomes inconsistent due to fabric barriers: expansion is often not reliable, and the penetration is also sometimes marginal based on the load and the barrel length. The environment of home-defense is important here. Bulky attire, unconventional angles, and locomotion are usual. The cost of those variables is more expensive with a caliber that exists on the border of acceptable penetration.
4. .410 Shotshell Fired From Handguns
410 handguns market a notion of a shotgun effect in a smaller handgun package. Theoretically, short barrels and non-optimal projectiles are more likely going to give non-uniform results and pattern dispersion may become pellets falling off a target the size of a torso at the distance of hallway. That generates no accountability problems, it generates solutions. The platform-sensitive even committed.410 defensive loads. One experiment using a Shockwave-style.410 indicated that certain loads retained the pellets close together but others threw the projectiles too widely to allow the projectiles to drop out of range, even when the penetration of particular projectiles (such as defensive disks) in gel was robust.
5. .380 ACP When Loaded Light
380 ACP should work, though it does not tolerate indolent ammunition choice. Aggressive expansion designs, low velocity, and short barrels can work together to bring penetration down to below what is regarded as defensive limits by most. In conjunction with low-performance loads, it has replaced itself as a caliber that appears modern on the outside, but acts like a compromise on the inside, particularly once heavy apparel comes into play to confound hollow-point performance.
6. 10mm Auto
10mm Auto is not a toy and that is just the beginning of the trouble. Full-power loads have the capacity to recoil and muzzle blast over a distance where most shooters tend to lose speed and accuracy when under pressure. That is more important in a domestic than in an outdoor trail, as over-penetration and missed shots are increased at a rapid rate when control is lost. Repeated gel work with other service calibers demonstrates the how little variation in expansion and penetration affects the results with barriers. The larger variable is the shooter with 10mm: “Remember that the best loads are not always the best to use in your defensive revolver when the effect of recoil is considered.
7. .38 Special in Ultra-Short “Snub” Barrels
The history of 38 Special is long, and the cartridge itself was not intended to fit around barrels that could hardly squeeze past two inches. With decreasing velocity, hollow points are more apt to become clogged and not to expand and loads that do expand may slip towards the low end of the penetration window. The revolver gel work, by Lucky Gunner, of a 2-inch class, with a 4-inch class barrel, throws out the reason why the length of the barrel cannot be overlooked. The same bullet may act quite differently when slow, and experiment with two barrel lengths stresses the possibilities of snub to increase inconsistency.
8. .44 Magnum
44 Magnum is very efficient in making deep impacts and striking hard. These advantages will turn into disadvantages in a home-defense scenario: fully exploited recoil, slow succeeding shots, and a high probability of penetrating the target with follow-up fire through multiple interior walls in case the shot is not entirely contained within the target. Home building is not bulletproof. A wall is usually a sheet of drywall and studs, and not much could be done to alter the simple reality that a magnum handgun shot has greater penetration capability than most indoor environments can safely accommodate.
The theme that is common with these calibers is not the stopping power as a slogan. It is stress performance: system reliability during ignition, sufficient penetration into clothes and control that hold the rounds in place. The cartridge is but part of the system in home defense–but the part which there cannot be bargaining over when the trigger is pulled.
