that's right fireman, that's basically what we do in BR to ensure best case alignment in the chamber and long life of the brass. You may need to try different FLS dies to find the "right" one that only does the minimum resizing or one that matches the chamber cut by your gunsmith; your gunsmith should know this.
Essentially, using a Stoney Point head space comparator (now Hornady) or similar, measure the fired case to get an initial measurement of the headspace and you check against this figure as you adjust the FLS die. When the case is resized to fit your chamber it should measure no more than 2 thou less than the initial figure. You should measure and check the progress on pushing the shoulder back (note the case shoulder measurement will "grow" ) as you wind the die down.
Also, you should remove the firing pin assembly from the bolt body, all you need is the bare bolt body to check the looseness of the resized case, this ensures the trigger is not engaged as you operate the bolt, you get much more sensitivity when you chamber the partly resized case. It is very difficult to ensure the correct feel with the firing pin assembly fitted.
Using a FLS die and the bolt body to check fit, you progressively wind the die down in very small increments until the bolt begins to close and you keep going until you get the bolt handle about 1/2 way locked, a little resistence is good and when the bolt handle flops down STOP, the case is FLS'd to fit your chamber perfectly.
Personal preference comes into it now, you can leave the die set with mild bolt closing force or at the flop point. You're choice, but it should not be too much force to close the bolt as to alter the rifle position on the bags/rest setup. You can now measure the shoulder set back and it should be around 2 thou less (maximum ideal shoulder set back) than the initial measurement on a fired case.
Remember, when the FLS die contacts the shellholder you have resized the case to fit EVERYONES chamber......provided of course the chamber meets the SAAMI spec's Resizing to a nice fit ensures good case alignment in the chamber and minimises the amount of resizing to ensure long case life.
hope this helps
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