I have read that may take brass two firings to fully expand enough to completely fit your chamber. Example- I am using virgin Lapua brass in a .243 that is brand new and back from having a new barrel installed. On the first trip out to the range, I sighted in the scope and did the standard ocw load development test. for round two of the ocw test to check for seating depth, I just neck sized the brass and went with the best load the target was giving feedback on. After the second firing I plan to use my gauges to measure the brass expansion to set my resizing die for bumping the shoulder back 1/1000th.
I just dont understand when firing a round that brass takes a second firing before it elastic enough to have the optimal chamber "foot print" for lack of a better word. for sake of discussion I am shooting loads that less than max and searching for accuracy instead of top velocity.
Then take it a step further for the guy shooting an AI cartridge or other wildcat.
Please enlighten me
I just dont understand when firing a round that brass takes a second firing before it elastic enough to have the optimal chamber "foot print" for lack of a better word. for sake of discussion I am shooting loads that less than max and searching for accuracy instead of top velocity.
Then take it a step further for the guy shooting an AI cartridge or other wildcat.
Please enlighten me