When a barrel has been set back and a new chamber reamed ideally are you trying to get the headspace set for minimum expansion of the cartridge? (if you are concerned with accuracy at all) How much expansion is acceptable? Does this expansion affect accuracy, or once the cases are fire formed does this in effect compensate for the extra space? My rifle is a M70 Win. and I have had an "accuracy job" done on it. Using the headspace insert on the Stoney point tool, I am getting .008 difference between a new Federal cartridge, and then the case fired in the chamber. What do you think? Thanks for your help....ol blue