I have a used Colt which came with a half moon carrier with an unshrouded firing pin and I have no idea how many rounds on the bolt. It works fine, but again I have no idea how many rounds are on the bolt so I’m planning on picking up a new bolt carrier group when I have the money and a good one is available. I know that its generally a bad idea to put a used bolt in a new barrel, but would it be a bad idea to keep that used bolt to use as a spare in the barrel it came out of?
Well, no one told me not to and a new LMT BCG is on its way so I’m going for it.
Use the search feature. It’s been talked about in depth numerous times.