About any good Hard Cast bullet of 250grn weight or heaver, loaded to about 850fps or more will take a bear down.
Hummmmmmm.........250grem 850fps,,,,,,,,,,,,,I can get that with a full case of Black Powder and a good crimp, and safe in a Colt or clone.
But then I oftedn hunt with the 45lc and BP just for the fun of it.
Greeenriver, (There's something about taking game with the old calibers loaded the way they were way back then.)