Bad habits, chamber a round and then fire it, then neck size if five times and then full length size the 6 time fired case to start over, when I start over I start with a new case, when I size I know the length of the chamber first, I then adjust the die with a feeler gage to prevent moving the shoulder further than necessary, that technique is not possible because reloaders do not know the length of the chamber then they put too much confidence in their ability to measure a case after it has been fired, again I measure the chamber first, and I think the neck die is cute, I own several, neck sizer dies are nice to have when forming cases for chamber I do not have dies for.
And I do all that work without a head space gage, but if I had a head space gage I would know what to do with it, I would use the go-gage by converting it to a go-to infinity gage (in thousands) and if I had a field reject gage I would use it to check head space from minimum length to go-gage, to no-go gage, to field reject and beyond.
And again, there is the demonstration, the case, powder, bullet and primer outruns the firing pin and escapes the firing pin by accelerating to a speed = to the speed of the firing pin, HOW DOES IT DO THAT? And it all happens before the primer is crushed, my firing pins crush the primer before before the case, bullet and powder knows their little buddy got crushed.
And the case is not grown to full size until it has been fired 5 times?