It's a Saiga-12 "assault" shotgun, like this one.
10 and 12 round stick mags, 20 round drums. No offense, but at closer engagement ranges (which is what I'm going to have around here), the shotgun rules over the rifle.
I got to handle (but not shoot) the Saiga 12 at the NRA party in AZ last weekend. Felt pretty good. You could probably buy several Saigas or a trunk load of ammo for the price of the fancy name brand.