Fire forming question

[bob4]

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.

 

[jimbires]

fire your brass and neck size only until it starts to get tight . then you can set up your full length sizing die to bump the shoulder .

 

[bob4]

fire your brass and neck size only until it starts to get tight . then you can set up your full length sizing die to bump the shoulder .

That's what I had thought.

 

[MagnumManiac]

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.