Bump firing is a waste of ammo. Personally I would rather use an AR-10 that fires 7.52x51 with the X-10 50 Round Drum.
The Israelis use suppressed Ruger 1022s to deal with this sort of threatening rioters. Hips, crotches, lower backs, after a few screaming fools writhing on the ground spurting blood the rest tire of the game.