Loading for about a year now, and rounds are shooting well and I'm staying competitive in matches with my loads, but not really sure about this. I'm measuring a fired case with the Hornady headspace gauge or shoulder gauge and it's typically approximately 1.625, now I was taught to just try to bump back .001 to .002 in resizing. So I had everything set up and was getting cases coming out at 1.624 to 1.623 and thought Ok swell right on target. After seating I gave rounds another check just for kicks and then found the measurement to be 1.620 to 1.622, What the @!$& ? Am I doing something wrong or missing something ? Im turning out the overall length I want (measured to Ogive) and all, and rounds are shooting fine but am just perplexed as to the change.