The Live Free Armory Challenger 9mm PCC operates on a straight blowback system and does not require a gas block and gas tube as traditionally found in other AR15s. The direct blowback system uses the kinetic energy generated from the discharge of the cartridge to push the bolt back and cycle the action. The Challenger-9 is compatible with standard frame GLOCK G17/G19 pattern magazines. The receivers are machined from custom 6061-T6 billet aluminum. The LFA Challenger utilizes a 16 inch barrel. These barrels are manufactured with the same quality and attention to detail as our AR15/AR308 you know and love. The free float handguard measures in at 15in M-lok compatible and free float handguard. – Magazine Compatibility Glock Compatable Magazines – Weight 6.7 lbs – Barrel Length 16 – Barrel Material 4150 Chrome Moly Vanadium Steel – Barrel Finish Black Nitride – Barrel Profile Straight – Chamber 9mm – Twist Rate 1:10 – Gas System Direct Blowback – Gas Block Type None – Receiver Set Precision CNC Machined Billet 6061 T6 Aluminum – Muzzle Device A2 Flash Hider – Muzzle Threads 1/2×36 – Receiver Style LFA 9mm PCC – Receiver Finish Cerakote – Forward Assist No – Dust Cover No – Handguard Style LFA Lightweight 15 M-Lok Free Float – Last Round Bolt Hold Open Yes – Bolt Carrier Steel Steel – Fire Control Group AR-15 Single-Stage Mil-Spec – Buffer Tube 6061 T-6 Aluminum Mil-Spec Tube – Adjustment 6-position collapsible – Stock Battle Link Minimalist Stock – Grip Thril Rugged Tactical Grip – Magazine (1) 17-Round Magazine (where available by law)