Balls do work well on B. Bear bear- from .45 on up. Personally, I wouldn't use less thna .50 on black Bear and not less than a .58 on griz - perhaps a .54 would be just fine, but then Lewis and Clarke found the .54's were a bit light. I don't know what charge they used and it could have been only 80 or so. That's about equivelent to today's 100gr. GOEX. We normally use 120 to 130 for moose with good results in a .54., but griz bite harder, I've heard. I found 165 turned the moose trick with the .69 and that is was a good 80gr. more than necessary. 100 to 120 worked just fine in the .75.,but 60 to 80 would have worked almost as well out to 100yds or so, but the .54 should have as much initial velocity as possible and about 130 to 140 would be about perfect for 2,000fps. I would also restrict the range to 50yds or closer with smaller sizes - oh yeah, only fast twist .54's shooting slugs Whenyousmack him, you want that slug and round ball to travel straight lines, not bounce around the bones.
: I have and have used cenrefires up to .50 on big game here, and they all work well, even a .32Spl. on black bear.
; The .45 centrefires are great all round bear loads, from fatory 45-70(405 only)on up. I no longer have a 45-70, but the .458 2" is quite similar to a .45-70 in a Ruger#1 and the .450 Alaskan, well I've found it's a shortened version of a .458 Winchester mag.- same capacity, same ballistics. The very incredible thing here, is that eventhe biggest .45 or .50 can be downloaded to or for whatever you want, even loaded for bear - any bear.
Daryl