Ya, you will need to slow that down for the AR impaired.... :) I saw Shilen has matched barrel and bolts for .223, but not .308. But then just buying "parts"... I do not see any other "matched" parts. And no "specs" to match anything to head space wise. Of course, these days there is no parts at all, but between carriers, bolts, and barrels, nothing is matched. Most people seem to have not problem mixing and matching, obviously with what fits. So how do I go about getting parts to assemble?