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.