^^^ I vote this ^^^
Was shooting 20 GA Rifled Foster slugs from a Mossberg pump not long ago. Heavy recoil. Dont think a North American bear will complain much about it being 20 gauge.
Seriously for hiking, ect... surely a large cal pistol on your hip and a can of bear spray would be less conspicuous, more effective, and less cumbersome than lugging around a shotgun even a 20 ga.