I once found myself in a conversation with an Alaskan charter captain on this very subject. There had been incidents that week of salmon fishermen in back country rivers being chased. His recommendation was a heavy caliber - a .44 magnum at least.
But, he said, "most people file the front sight all the way flat, flush with the barrel."
Puzzled, I queried "why in the world would they do that?"
His answer - "that way it doesn't hurt as badly when that bear takes the gun away from you, turns you around, and shoves it up your (fill in blank)!"
Okay, okay. He got the tourist fisherman to bite. True story.