If you are equipped to hunt bear, you are almost certainly not using an automatic. Any caliber high enough to drop a bear in one shot (which you want to do as to not ruin the bear) would break your arm into slivers were you to fire it at automatic speeds.
I'm no gun expert, never even fired one, but it seems there are many guns that would fit the bill. Example: http://www.youtube.com/watch?v=WOoUVeyaY_8&feature=plcp in particular, watch at about 5min point to see the (lack) of) recoil, put slugs in it and I would think you'd have no problem stopping a bear. This guy's You tube channel in general contains a lot of things that would not have a problem stopping a bear. That said many are not your average hunting equipment either, but I don't think anyone goes out with the plan of getting close enough to a bear to use a shotgun.
