I need to ask a really stupid AR question....

Mar 25, 2008
...that I've never seen discussed. Are AR-15 bolt carriers and bolts interchangeable? Say , as an extreme, for some reason a bolt-carrier for a 450 Bushmaster was damaged? Could you take the bolt carrier from a 223, put the 450 Bushmaster bolt in it, and run the 450-rifled barrel? Or are the bolt carriers specific to calibers as well and the 450 Bushie bolt carrier itself is bored differently somehow?

I ask because I saw a KAK add tonight selling complete BCG's and also separate bolts of various calibers. I'd never seen replacement bolts sold separately, so I'm wondering about mixing them (recognizing the barrel would have to match the bolt).
For the most part yes, but as some things may wear in there maybe some tolerances that may cause troubles. I think it's best to just start with everything new.

I try not to mix bolts and barrels (receiver extensions really) after they have been shot.
There are also some unique bolts/extension etc that wont interchange with anything else.
All standard AR15 bolt carriers are made the same as far as dimensions go. So yes you can swap different bolts into the bolt carrier. You do have to take into account for normal wear on used parts and make sure they are still within spec.

We were always told in the Army to never swap complete bolt carrie groups or even just the bolts themselves between rifles. The reason is that the bolt and barrel extensions will wear in together after a while. Switching BCG's between rifles with high round counts could have head space issues.