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Old October 8, 2012, 07:54 PM   #2
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Join Date: September 9, 2008
Location: Woooooshington
Posts: 1,797
The fired cartridges measure 1.4575 . I assume I want to set up the die to push the neck back .002 to .003 (this is what I read in the manuals). So this would be 1.4545?
I assume you mean you want to bump the shoulder back, not the "neck"... and yes, your math is correct. But...

There are lots of variables here. The fact that it's a AR... the chamber, the dies, lube, you and your abilities, condition and quality of the brass etc etc.
The problem is that if you bump the shoulder back, from a fired case dimension, only .002"~.003" it still might be overly snug in the case body diameter.
To be on the safe side, I'll say that if you want to avoid working the brass any more than necessary, you start by going up a few thousands from your unfired (1.4505") ammo... if that cycles reliably, then add a few more thousands from there. Once you see signs of cycling issues, back down .002" and call it good.

In other words, go up from minimum rather than down from max.

Shoulder Drive Nicholson Club
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