Just a few thoughts on headspace and ammo. Several years ago I purchased a 300 pc lot of unfired Remington cases. Checking the head thickness on a fair percentage most were several thousandths of an below the .064 max. With only a few that were .063.  On a 50 pc bag of Grafs unfired cases almost all were near the middle of the tolerance with the largest about .003 below max.
Since getting Remington in the future may be difficult and Grafs seems readily available having a bolt chamber combo that is just a .001 too small may be no issue at all.
If you have a way of checking a batch of cases for effective head thickness you could find the largest one insert it in the chamber and check for free play. Your thickness gauge that can move around on the bolt is not the best because the barrel and bolt can have extensive wear on the case rim and no wear off the center. My old take off barrel has several thousanths wear from case rims. Outside that area is factory bluing. Same thing on the bolt but to a lesser extent.
When I mentioned effective thickness of the case, you could have a rim thickness of .061 and a couple of thousanths of "tilt"
on the rim from the case body axis effectively making it .063".
That is why I made this holder for gauging the rims.

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