So I screwed on my new Criterion 223 rem match the other night. I set the headspace pretty close to minimum. Go guage closes fine, but even 2.5 thou of cellphane tape will prevent closure. Did you know that SAAMI allows a massive TEN thousandths of headspace tolerance in the chamber? It's true. The Forster no-go I have is 1.4666" and that's still 0.007" shorter than max SAAMI spec. So I'm sizing some brass last night and trying to size it *just so* for this new Criterion's chamber. My comparator shows the go guage as 1.4565". It's wrong, but since it's just for "comparing" it's OK. I'm trying to set the headspace for just a tiny bit of squeeze, so I targeted 1.4585" on the comparator. Eventually I got there. In a tray of 50, over half the cases sized exactly to that value. The bolt closes with just a tiny bit of friction, just a very subtle jam, which is exactly what I was going for. This slight interference in headspace should assure that the case centers itself in the bore. But even though these are all the same headstamp AND they were all fired in the same rifle AND they were all the same charge of the same powder, I still had a ES in headspace of nearly 3 thousandths. The a handful of cases came in closer to 1.4600". One or two were as short as 1.4570. This is with the die locked down, the press a hard stop, and no source of variation other than the brass itself. Interesting that there is that much variation just in the brass springback.