Adaptive Tactical recently announced it's offering its Sidewinder Venom Shotgun Magazine Conversion Kits for Mossberg shotguns. These conversion kits enable the 500 and 590 pump-action shotguns to be loaded with the Adaptive Tactical's 10-round rotary magazines and five-round magazines.
Adaptive Tactical introduced its redesigned Sidewinder Venom concept in January 2012. I've never seen it before, but I'd give it a whirl. It does look like it would be right at home in an "Expendables" movie.
These shotgun magazine conversion kits can installed at home and includes either a 10-round rotary or five-round box magazine, forend with action bars, magazine tube, barrel clamp, forend grip, M4 stock, cutting tool and installation guide. They are available in black, DCS A-TACS, Tiger Stripe Desert Digital, and MultiCam. They cost $340-$400.
Adaptive tactical also offers pre-configured Maverick 88 security model shotguns with all the trimmings for $650-$720.