there's been a few questions of late related to full length sizing and checking headspace so I thought it might help if I quickly show how I set up my cases when full length sizing
firstly I take the case measurement, 83.02mm, I know sh!t photo but I'm in a hurry
then I take the firing pin out of my bolt so I can check the fit of the case in the chamber without resistance
I then check the fit of the case in the chamber
the bolt will not close on it's own but is not hard to close, the case is the same measurement as my dasher go gauge
I keep adjusting the fls die in small increments to set the die to bring the measurement back 2 thou/ .05mm smaller than the first measurement
I got 82.96mm, close enough for me
then check the case fit in the chamber
the bolt falls down with the 2 thou smaller measurement
this is the way I set up my fls die my cases last a long time