CALIBER:.450 BUSHMASTERUPPER RECEIVER:FORGED A4BARREL:16 INCH STAINLESS STEEL, 1:24 TWIST, CRYOGENICALLY TREATEDMUZZLE DEVICE:RRA OPERATOR BRAKE, 5/8-32 THREADGAS BLOCK:LOW PROFILE GAS BLOCK, MID-LENGTH GAS SYSTEMHANDGUARD:RRA 13 INCH EXTENDED LIGHTWEIGHT FREE FLOAT RAIL, M-LOK COMPATIBLEINCLUDES:BOLT CARRIER GROUP, CHARGING HANDLE ASSEMBLY AND ONE 5 ROUND MAGAZINE