I shot black bears this year and last year with cheap Foster slugs out of my 12 gauge Winchester 1300. Over bait, that's all you need.
Neither bear was particularly large - in fact, they were both small - but the holes the slugs left would have killed a moose just as easily.
One nice thing about shotguns - if you have to track a bear, especially after dark, it's a lot handier than a scoped rifle.