Adams Arms' proprietary gas-piston operating systems mechanically actuate the bolt carrier external of the receiver. P1 model features ergonomic mid-length handguards, standard Picatinny adjustable block piston system, tactical stock and grip with QD mounts, enhanced triggerguard. Barrel lengths and chamberings: 16 in. (5.56). P2 model includes ergonomic free float rail, P-Series Micro Block piston system. P2 barrel lengths and chamberings: 16 in. (5.56); 16 in. (300 BLK). P3 line features Proof Research carbon-fiber-wrapped barrel, jet comp, ergonomic free float rail, and P-Series Micro Block piston system. Other features include CMC Flat Bow trigger, a rubber ergonomic grip, adjustable stock with cheek riser. P3 barrel lengths and chamberings: 16 in. (.223 Wylde), 20 in. (.224 Valkyrie).