The Adams Arms P1 model is the perfect platform for shooters who enjoy building and customizing their rifle. The P1 model includes our Picatinny Railed Gas Block with 3 adjustable settings M4 furniture and the SB Mini Brace. The P1 is your Piston Driven foundation ready to be customized to fit your needs. - Upper Receiver: A4 Flat-Top Forged - Barrel Length: 11.5 - Barrel Contour: M4 - Barrel Material: 4150 Chrome Moly Vanadium Steel - Muzzle Thread Pattern: 1/2-28 - Chrome Lined: No - Barrel Finish: QPQ Melonite / Black Nitride - Twist Rate: 1 in 7 - Chamber: 5.56x45mm NATO - M4 Feed Ramps: Yes - Bolt Carrier: Full-Auto Rated 1-Piece w/Integral Piston Strike Face - Muzzle Device: A2 Flash Hider - Gas System Length: Carbine Short Stroke Piston Operated - Gas Block Diameter: 0.750 - Handguard: M4 Handguards - Sights: None - Grip: A2 Grip - Trigger: Standard G.I. - Stock: SB Mini Pistol Brace - Weight: 5.7 lbs - OAL: 28.5 collapsed