case length

[jdefranc938]

Hey guys,
When I get my virgin brass I try to trim the necks to 1.840". After a firing or 2, the case length is between 1.844 and 1.859. If I retrim it to 1.840 and refire it, it continues to elongate after each firing. I understand this is normal to a degree. But should I always be retrimming it? I don't wanna weaken the brass. Any input here would help. Also, will this change consistency?

[jo191145]

Excessive case growth is usually a direct result of excessive full length sizing (bumping the shoulders back to far)
Do it enough times and the brass will reach a point where it has stretched/thinned out just above the web.
A bright ring will appear (not to be confused with friction marks from the chamber)
At that point the brass is ruined. One more firing cycle and you'll most likely have case head seperation.

I FL size my brass every firing. I can't remember the last time I had to trim my brass.

You will get a slightly different measurement between fired and FL sized brass.

Did you ever get that die set up correctly?

[Rick in Oregon]

jo1911 is right, but why waste time trimming virgin brass when it will all change length upon the first firing?

Best to just neck or F/L size new brass and not trim till it's been fired once. THEN all your cases will stay within about a .002" length range together. Keep that lot segregated, and you'll not have to trim them for about 3 firings or so. You do not have to trim every time you load if all cases are under max length. Chances are your chamber is much longer than book max anyway.