I recall reading an account of a grizzly attack in Alaska from a few years ago. The shooter had a Ruger Alaskan, double action revolver in .454 casull, with ammo he hand loaded himself. The shooter was not hunting, but was walking and carrying the revolver due to recent bear sightings in the vicinity. The grizzly came out of the brush from about 20 yds and charged. The first shot missed; the next 4 hit and the sixth round had jump crimped and failed to fire. The grizzly skidded to a stop a few feet in front of the shooter. Another hiker, was a few hundred yards away, and out of view. She reported hearing shots fired so rapidly, she thought it was a burst from a machine gun. There have been a lot of different postings about this story, some more detailed than others. I can't find the original account of the story, but the link below is a pretty good one.