The Old Man killed a significant number of grizzlies over the years, and most of them were killed a 300wm and 180 gr Winchester soft points. Relatively soft bullets at relatively high velocity.
That said, none of them were 9’ brown bears (although at least three of them were better than 8 1/2‘ grizzlies).
Don’t overthink it too much. Just get close enough and break bones. A 3 legged bear is slower than a 4 legged bear, and a 2 legged bear is better yet.
