Backpacker killed a grizzly in Denali with a 45 acp. Eskimos kill polar bears with 219 Zippers & other 22 centerfires all the time (where they get the ammo, I don't know).

I recently started shooting a 40 S & W and I'm impressed. It should work for black bears==now, grizzlies are something different.

In 1989, I was elk hunting in NW Montana. They had just found some grizzly droppings; first in quite a while. I asked the bio what he found in the droppings. His answer: "Black bear claws"