The problem I run into with AR barrels is that I have yet to find one that has too great of headspace but I have found several that are too tight. You need a go gage to determine that. For me...working with new barrels with assembled barrel extension...a Go gage is more valuable than a No Go Gage. But I still use both.
Initially, I bought 6.8 SPC Manson gages that had the extractor relief on the gage's full diameter rim so that the gage could be used with an assembled bolt, but it was a problem trying to orient the gage relief with the extractor. Now, If I use these gages I disassemble each bolt and check with it's matching barrel extension and have had better results. If I disassemble the bolts I find it goes faster with fewer false readings.
However in .223/556 I use Forster Gages that do not have the extractor relief but they have a reduced diameter rim to clear the extractor. They seem to work OK but I have gotten into the habit of just taking all my bolts apart to be certain that the ejector or extractor are not having an influence on the headspace check.
The real issue is what are you going to do if you find a tight headspace barrel? You "might" be lucky by swapping bolts but most likely you will need a chamber reamer at $160+ each.
HTH
Kerry
