Do NOT -- repeat NOT -- set the sizing die to match any chamber GO/NOGO headspace gauge.
Similarly, do NOT set the sizing die to match any unfired commercial ammunition.
If you are going to set up the sizing die at all, use the "bolt-just-closes" dimension that you get
by gradually squeezing the sides of a fired case in using a gradually screwed-in sizing die (until the bolt
won't close at all unless you screw it in some more.)
If for some reason you never get to that bolt-won't-close point, just use the largest dimension that case
showed before the die began to finally push the shoulder back.