Was reading AK Fish and Wildife's mag a long time ago and they took up the question of what hand-held weapon would provide guaranteed survival from a Grizzly charge. They limited to self defense, close range (you were really in danger and not just scared), and when you hit it most anywhere it stopped.

Their conclusion is that such a weapon did not exist. The kicker was the guarantee of stoppage. Maybe we know more now but it was food for thought especially for my friends who worked streams up there.