Fire forming question

bob4

Well-Known Member
Joined
Nov 10, 2012
Messages
549
Location
Naples Fl.
Do you keep firing brass and full sizing it without bumping shoulders until it shows signs of harder chambering thereby thinking it's time to bump .002? Have a new to me /nicer rifle, and want to do this right without pushing 2000 rds through it. Supposedly and I believe him, only 60ish factory rounds through it.
For those curious it's a Cooper 270, 24 inch stainless.
 
I don't size until the 3rd firing or when the case has 'feel' as the bolt is closed with the firing pin assembly is removed.
In my experience with full power loads, 3 firings has filled the chamber sufficiently.
Then, depending on use, I measure the head to datum and size until a case is .001" less (comp rifles) or .002" less (hunting rifles). This, with spring back, gives me a chamber sized case or a little less, and a case .001" less than chamber size.
I have also used .002" bump, sizing .003" to allow for spring back.

Cheers.
 
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