I bought the case length measurement plugs from Brownells. Put them in a lightly tightened neck that is trimmed way short. Insert into chamber and bolt in. Eject and “walla” you have your max brass length. I have found my chambers have max brass lengths anywhere from 15-45 thousandths longer than book max length. I make a note for each individual rifle of its max brass length and as long as I am 10 thousandths lower than max, I don’t trim. I hardly ever trim brass now unless I am really fine tuning a load.
https://www.brownells.com/reloading...clair-chamber-length-gage-prod32925.aspxI carved one out of wood, prior to finding Brownells done thought of it too. Good little tools.
(That was when I had one rifle and was self-teaching myself to reload and didn't have a case trimmer. I was trimming with a deburring tool. Had read that a kaboom was a possibility with cases too long and it seemed a sensible way to figure out how long was too long. Nowadays I tend to trim a little short, and collet neck resize and retrim infrequently. But, thinking this over, trimming too short could be hampering my accuracy? Will have to take another look at it.)
