There are two acceptable calibers* for True Americans. .45 ACP and .357 magnum. Anything else is wrong, unless the question is "what caliber won't hurt my girly wrists and won't make me look fat in these jeans?"
The FBI results are pretty much what I figured they would be. It is all about shot placement in order to drop someone with one shot no matter what the caliber. That movie stuff where you see someone blown backward off of their feet by a shot from a firearm is utter nonsense! There is not enough mass and energy even in a 50 BMG to do that. Has anyone ever seen the Mythbusters episode where they tested this? They had a pig carcass barely hanging on a metal hook and shot all kinds of calibers at it and it didn't budge.
There is a reason for this. See Newton's Third Law of Motion.
Started out with 9mm liked it shot it well, went to a .40S&W and really liked it. A little snappy but manageable, and for a long time thought I'd never want a.45. Eventually got one and don't shoot anything else. Can someone really stay standing after getting hit by a 230 grain sledgehammer?