Ok, so I just started using a set of Sinclair headspace gauges. I've been resizing some once fired .204 Ruger brass and I'm a little surprised to see that no matter how far down I take the resizing die, the shoulder will not bump back.
No matter how far down you adjust the die? Logic is logic as Truthful James said. After the die contacts the shell holder that is it. The two can not get closer once they make contact. Then there is the ability of the case to resist sizing, the cases ability to resist sizing can be more than the press can overcome; that is the reason I check the gap between the bottom of the die and top of the shell holder.
Then there is that problem; bad habits, a reloader should measure before firing and again after firing to determine the effect the chamber had on the case. After firing there is measuring before sizing and again after sizing. I suggest the reloader save a few cases for compassion. If the case chambered and fired the reloader should save a few of the unfired rounds for comparison.
F. Guffey