Black bears or dangerous bears?
Black bears aren't very tough, so anything with 30-30 or 44 Magnum power will do the job.
Dangerous bears are, well, dangerous and I think that I'd want to be shooting the most powerful cartridge that I could handle well if confronting them in heavy brush at close range was in the cards. As a minimum, I'd be thinking more along the lines of a 9.3x62 with 286 grain Partitions.
Jeff
