I wounded a badger at about 20 yards with a Colt 1911 Gold Cup National Match, .45acp, 230gr fmj.

Badger then ran straight at me. I kept shooting and the badger slowed and died 10' from me with 4-5 entry wounds.

FMJ is admittedly inefficient but with a grizzly/brown bear I wouldn't have gotten three rounds off. And with a .44 or .454 etc would probably not have gotten off two rounds. My faith in stopping bears lions tigers etc with a handgun is low.

A Montana rancher with grizzly experience pointed out that in a bear encounter you are likely to literally be shooting the bear off you. Consider that if an auto pistol slide presses against anything, the gun is tied. Won't cycle. But reportedly Glock 20 10mm pistols are considered a good alternative to big revolvers.

Bear spray (pepper spray in large cans) is proven more effective bear defense, statistically, than guns. I owned forest land in British Columbia in an area with a dense population of grizzlies. Walking my property I could dangle a can of pepper spray on my finger like it was car keys. With pepper spray, you can immediately deploy it, basically can't miss, and it is proven effective at driving off bears. Occasionally a determined bear returns. It seems to me that the pepper spray is a rapid, almost sure-fire way of making the bear back off, giving you time to ready a firearm. And instead of a 30mph rushing bear, you're then aiming at a hesitating bear. Watch video of charging grizzlies and brown bears: their heads bob around and would make a really tough target.