from bolt face to the chamber’s shoulder, it’s slap full of bottleneck case. From there, measure and record for all future, the case head to case shoulder reference length for zero headspace, and adjust the dies to bump ‘um, or not, to whatever amount shorter.
I am lucky; my chambers have head space, I measure the length of the chamber from the datum to the bolt face. And then there is the case; my cases do not have head space, I use the case to off set the length of the chamber. and then there is anything left over; the difference in length between the chamber and case from the usual suspects as in shoulder to the bolt face and the shoulder to the case head is clearance.
I can have minimum length/full length sized clearance, for the 30/06 that would be .005" in the perfect world. And then there is the chamber that is filed gage length from the shoulder to the bolt face; that chamber is .014" longer from the shoulder to the bolt face than a minimum length/full length sized case. To reduce clearance I form the case with additional length between the shoulder of the case to the case head.
F. Guffey