.357 Mag or better will do for black bears. A .44 Mag is better.
We have brown bears around here. Are they the same? It’s mountain lions I’m skeered of. Seen their scat (huge!) and paw prints (big!) on our property. Neighbors trail cameras have caught pictures of them. DH has seen them crossing the road a few times. Very rural of course. We’re near a small branch of river so lots of animals around.