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