If you can't find a new one and opt for a used one off the EE forum, please ensure that you get a positive ID on the bolt's manufacturer. I didn't....(my fault for not asking the right questions, I'm a trusting soul) and was sold a BCG that was "unmarked but probably LMT as it came out of an LMT upper". Turned out it's a Norinco BCG and I was out $185. Caveat Emptor.
Whatever floats your boat... they all work just fine in semis.



























