A .45 Will Stop Them...But You Better Have Some Pellets

Alaska: Backpacker Kills Aggressive Grizzly Bear

quote:

The man fired nine rounds from his .45 caliber, semiautomatic pistol at the animal, which then stopped and walked into the brush.

If he had a single stack with 8 plus one in the pipe, that would mean that he was out of ammo. For bear you need something with a little more FPS than a standard .45 round. Some +P rounds in a double stack would probably be a better choice next time.