RE: Caliber for Bear protection!
The reason black bear attacks are up is that 'civilization' is encroaching more and more into their territory, AND the people moving into these developments generally have an opinion of bears reinforced by the 'cuddly-fuzzy' image fostered by what they see on TV... They don't realize a black bear is a potentially deadly wild animal!
The requirement for protection is to use a gun that shoots hard bullets of good sectional density that YOU can shoot fast & accurtely under the stress of a close encounter. Even a .45 with GI hardball ammo will suffice, because you have to get the bullet into the critter's brain right now to stay in one piece.