the best response was the poster that mentioned head on attacks
As apparently, that would be your encounter, a charging bear, which seems that all other post on how we used to hunt them back in the day etc etc is out the window, thread was, as I recall, what to carry in defense of bears, not the best bear hunting firearm. So a charging at you bear presents, apparently, primarily a head on shot as they're all head coming at you (especially since you are not laying down shooting but probably standing upright), buckshot for a bear's head??
I shot a pig, not even a hog, but a wild pig, at point blank range with my Colt 45acp, two rounds clean through the head, CCI lawman FMJ rounds, and the pig kept going, albeit would have died anyway as both were lethal hits, pig wasn't charging me but merely trying to escape. Killed but didn't stop. Apparently there is more to stopping then merely putting a couple small holes through a large hard cranium. I'd opt for slugs only for defensive shotgun load for bears.