I would determine the length of the chamber first, then form, then fire as opposed to FIRE FORMING, chamber a round, pull the trigger. It is a very short distance from purchasing a press, die and shell holder to fire forming. In the perfect world new, minimum length, first time fired cases are used. Problem for reloaders? The go-gage, no go-gage and field reject gages are fixed in length meaning a minimum length/full length sized case will chamber in the perfect go-gage length with .005 to spare, in the perfect world minimum length cases when fired in a go-gage length chamber the case will be ejected .005 longer than minimum length, .000.
Then there is the machine gun fired case, no one the length of the chamber from the bolt face to the shoulder of the chamber, no one measures the length of the case from the head of the case to it’s shoulder, therefore no one knows the effect the chamber had on the case length when rejected.
If the shooter measured the cases before firing and again after firing and finds the case length has increased .004 the person doing the measuring can safely say the length of the chamber is no go-gage length. It helps to understand when measuring the new, unfired, minimum length the measurement is .000 for comparison purposes, the .009 reading includes the original .005 difference between a go-gage length chamber and a minimum length chamber, the additional .004 should be attributed to a long chamber., I form first then fire, meaning I can not adjust the chamber length so I adjust the length of the case to off set the effect the chamber will have on the case when fired.
I am a big fan of cutting down on all that case travel.
F. Guffey