I am told Alaska wildlife employees carry 12 ga shotguns and load 600 gr 1500 fps Brenneke Black Magic slugs for handling problem brown and polar bears...
AK Fish & Game travel in groups of 2 or more, with one of them carrying a 12 Ga., #1 buck.
A shotgun works very well for the quick aim needed and no need to shoulder the weapon. Pumps are also very weather tolerant.