"An infinite number of monkeys banging away at type writers for an infinite period of time will eventually reproduce Hamlet" Thanks to discussion forums we now know this to be untrue.
Lol time to put you out your misery mate I know exactly what I did now, as you know I was trying different cases so I decided to measure case length alone so popped the anvil on to give a good base with the comparitor still on as used the base of the cartridge on this side and neck on anvil side zeroed the calipers with both anvil and comparitor on , then went back to measuring OAL took anvil off and never zeroed the calipers again