An old buddy of mine was deer-hunting in the Catskills of NY with a single shot muzzle-loading rifle. He rounded a friend's barn and came face to face with a slightly wounded black bear. Perhaps if he had a repeating rifle, he might have done otherwise, but he slowly started backing away from the bear. The bear slowly started backing away from him, until they were about 30 yards apart and then they both ran like hell(in opposite directions, of course).

In a less humorous vein, when I was stationed in Alaska just before statehood, a hunter back-packing 2 fresh black bear skins was ambushed and killed by a grizzly. It was believed that the grizzly was black bear hunting too. Larry