As most of you know I am a firearms instructor. Talking about guns and ammo and personal defense is something I enjoy. The topic just never took root in our previous venue, but maybe that was because of the very young international membership. Here, though it seems a lively discussion has already started in a completely unrelated thread. Shall we continue here, gentlemen?
The debate on what is the "best" caliber for self-defense has been ongoing since there have been firearms. As technology has change so have the arguments for or against different calibers, gun makes and models.
At one time, when almost all bullets were either solid lead or a full-metal jacket, FMJ, over a lead core, size did matter. With FMJ the size and velocity of the bullet made a difference to the terminal effects on the target. A large hole was better than a small hole. Higher velocities produced better terminal performance.
With modern bullet design the profile of the bullet, e.g. full-metal jacket (FMJ), jacketed hollow point (JHP), jacketed soft point (JSP), round-nose lead (RN), solid, polymer-tipped hollow point (PHP), and many others is more important than the caliber/diameter of the projectile.
Modern handgun ammunition that is designed for self-defense is all designed to produce similar terminal performance on the target/bad guy.
.45 ACP, 10mm Auto, .40 S&W, 9mm NATO, .357 Mag, and .38 Special S&W are designed to expand to about .60 caliber, penetrate 10"-14" into the body, and dump all of their energy into the target without passing through the target. While the energy dump into the target will vary, the terminal performance is similar enough that choosing a .45 or .40 over a 9mm doesn't make much difference.
The 10mm Auto and the .357 Mag are outliers in that they are designed to be overly powerful. Lots of power, not as easy to control. Pistols in .380 ACP, aka 9x17 in Europe are suitable for self-defense but are not part of this discussion.
For me, the difference is in magazine capacity. Using full-size Glock pistols as a baseline, I offer the following.
A Glock 17 (9mm NATO) with a standard capacity magazine holds 17 rounds of ammunition.
A Glock 22 (.40 S&W) holds 15 rounds of ammunition
A Glock 20 (10mm Auto) holds 15 rounds of ammunition. A favorite choice for bear country
A Glock 21 (.45 ACP) holds 13 rounds of ammunition.
If I am in a gunfight ammunition is like air, nothing else will do. The more the better. I would like 17 opportunities to save my life verses 13.
Additionally, the "hotter" calibers such as 10mm and .40 S&W are not as comfortable or controllable when compared to the 9mm or .45 ACP. The 10mm is especially hard on slides and frames, and shooters. That is why the FBI dropped and then helped develop the .40 S&W, essentially a 10mm Short.
While the choice of police agencies in the 80s, 90s, and early 2000s, was the .40 S&W "because it was developed by the FBI" most agencies have been going back to the 9mm for capacity and shootability.
I look forward to your comments.