IMO, black bears arent any harder to kill than a deer.
I packed a .280.....
Or a 270.....
Course I mostly used Bitterroots and Nosler Partitions;both of which make it kind of like cheating.....and have found what Pat and Dober have found...namely that black bear die about like deer do to similar hits.I have never observed them to be "tough" to kill,unless hit poorly, which should not surprise anyone.