That's why the 9mm is getting so many bad reports from Iraq. If you use FMJ ammo then you tend to get over-penetration with the smaller calibers. The .45 is working out better for them because it makes a slightly larger hole and it tends to expend all of its energy within the target, i.e. it goes in but doesn't come out.

Using a good hollow point bullet changes things dramatically. Something like a Winchester Ranger T Series SXT has a lot of stopping ability and I wouldn't hesitate to carry it in my .45acp for protection anywhere I normally travel from municipalities to mountainsides. Sometimes I carry my 1911 and sometimes I carry my S&W 1955 revolver.

However, I don't normally travel to big bear country and I believe there are much bigger and better choices than .45acp for use against large bears. When you get to these larger calibers you're choices are pretty much limited to a revolver, the rare auto-mag types excepted. Revolver shooting is very different than any other kind of shooting and, within revolvers, single action and double action shooting are differentiated even further.

Most people agree that the big stoppers begin with .44 Mag and go up from there. I've never shot anything larger than a deer with a pistol but that sounds reasonable to me. However, I wouldn't want to carry something so big and so heavy that it makes it difficult to quickly draw and use. The big S&W canons, the Linebaughs, and the guns chambered in .45-70 and .444 are so big that I wouldn't carry one as a secondary weapon. A 15" long, 4.5 pound revolver may be fine as a primary weapon but a secondary weapon should be out of the way till needed and then quick to deploy. I have read several reports of big bears mauling a victim who didn't have time to use his weapon in defense.