10MM has proven itself. The small-medium grizz around Chicken won't be a problem... besides, if you're hunting RC860, you'll have A LOT of company, and I doubt too many bears will hang around.
I'd never carry a 500SW when hunting. To big, too expensive.
I carry either my Glock 20 10mm or my Redhawk 4" in 45 Colt and do not feel undergunned.