Google "old Mose"
I just looked, based on my memories of an article about him I read in a gun magzine a long time ago. The one that I just read told the story pretty well, but left out details about the gun that got him.
From what I remember, it was a .30-40 Krag. 1,000lb grizzly downed by a .30-40 Krag (although if I remember right, it took several shots).
I think I'd set my minimum grizzly standard at .30-40