Just to toss out a few other quick items to peek at: If your rifle has been bedded, be sure that only the back of the recoil lug is tight against the bedding. The sides of the lug and the front of the lug should not touch anything. Also, the barrel nut should not be touching anything. In addition, check (with a dollar bill) that your tang is free floated. If not, remove any stock material to have your tang not touching.
One other question: What brass are you using, and do you ever measure the diameter of the neck thickness of your brass?
Dave
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