My local mountains are full of black bears, and they aren't particularly fearful of humans! I carry a .44 Ruger Alaskan or 329NG, and don't particularly feel the need to drag around a long gun when hiking, but I do keep a shotgun in camp.

I think a Foster slug or even 000 buckshot would do the job on a black bear, but I am thinking more about the future when we might be back in griz/brown bear country once again.