How many rounds of virgin brass needs to be fired out of a given chamber before you start to get an accurate measurement on chamber size before you can get a good read on shoulder bump on a case. I have been reloading for several years and reading this forum for a long time I’m just a novice looking to get the best out of brass life. I have read on this forum that brass will not reach its full expansion in one firing. Just curious and I know there are loads of variables at hand just wanted some good advice. Lots of knowledge on this site. I have purchased the Hornady kit and was looking for guidance. Thanks in advance.