The best AR12 shotguns are listed below. The AR12 (or AR-12) is a shotgun built on the AR-15 platform. Shooters enjoy having the similar control to the combat rifle they are familar with. 12 GA is by far the most popular caliber but they may be available in 20 GA or 410 Bore. Looking for ammo as well? Browse our selection of defensive ammo for your new AR12 here, or all 12 GA ammo here.