Guys, I bought a used AR yesterday and would like some help identifying if it is a complete factory Bushmaster rifle or a lower with a franken upper. FSB reads: G02(R1)1 and does not have a bayo lug Pretty sure this brake is not factory as the pin holding it on is far too wide and not centered to be something from the factory. It works great and reduces all muzzle jump while shooting offhand. Barrel markings Wanna kill these ads? We can help!