My experience with the large frame AR is only over a couple of barrels and bolts and this is opinion rather than know for certain. I have not seen a .308 AR barrel and bolt headspace on a .308 GO gauge ONLY. Yes, I understand that's safe and somewhat expected, but optimal for accuracy? Even my old Franken 700 with a VS barrel won't close on a NO GO, and it has a throat a mile long. I agree with the person that said to bump your fired cases shoulders back 3 or 4 thousands and go from there.
I think the problem lies in the fact that the average somewhat mass producer of .308 AR barrels is always taking into account that somebody might try and shoot 7.62 from it. How is it that GAP produces a semi that shoots? I think it's because they're chambering and headspacing those barrels. Then again I've never heard anybody say my .308 GAP 10 won't chamber this vintage South African surplus I've been sitting on, so I don't know for certain.
I've never heard anybody say what their Lilja or Krieger headspaced to, so that would be good info to have. I have no personal experience with them, but I think that Noveske also has it down because I remember reading that they went in and cut their own chambers. This also leads me to believe that those rare and elusive M1A rifles that really do shoot have tight chambers, like a friend's SA. It will only close on a .308 go gauge.
And that M1A has the heaviest barrel possible. I don't think it's realistic to expect stellar 5 shot groups from a lighter weight barrel. If I were doing it again I would contact Brux to make me a .308 barrel, tell them exactly what I expected regarding chamber dimensions and ship them my bolt.