I receive many emails asking, in essence, what the "best" self-defense caliber might be. (Those emails, in fact, have served as the motivation behind this series.) The correspondents are probably expecting sage advice, the wisdom of years, a sort of Ballistic Oracle. What they get is a non-commital "it depends!"
If you take nothing else from this series, take this: there is no such thing as "best" – there is only "suitability for purpose."
Why is that? As we learned in the first parts, there is a pretty large envelope — caliber, weight, and velocity – of performance criteria that have shown themselves to work well. Thus, any cartridge you select within that envelope is likely to do the job, as long as you do yours.
That’s the most important part: that the gun in question enables you to do your job. It is the first place you should start. You need to be honest with yourself, accurately assess what you can and cannot handle. Remember that a self-defense scenario often will call for multiple, rapid, precisely-placed shots. Can you do that with the guns that you’re considering? Really? Be honest with yourself!
I see many people who are talked into a gun that is touted as a "better stopper", but who are unable to handle it to the standards given above. Most of this is technique, and technique can be learned, but everyone has some upper limit. Remember: only accurate hits count, and you should strive to maximize your hit potential. As we’ve explored, power is irrelevant if it doesn’t get to something important!
Once you’ve passed that hurdle, the choices almost make themselves. In any given cartridge, if you pick a hollowpoint load in the middle of the caliber’s normal weight range, you’ll generally have most of what you need. There are exceptions, of course: at the lowest ends of the energy spectrum (say, standard .38 Specials) penetration becomes an issue, so you should tend to the heavier rounds. At the other end (the heavy magnums), the more powerful loads often need lighter bullets to limit penetration and enhance expansion.
For everything else, stay away from the lightest and heaviest bullets, pick a decent hollowpoint, and you’ll most likely be just fine.