Belted Magnum Reloading and Headspacing question, first firing of new brass

[cdherman]

OK, have a new Proof Research 7mm RM barrel that I just screwed onto my 110 action (was a LR Hunter in 25-06) fixed bolt face etc....

I have never headspaced a cartridge off the belt before. And I don't have any fired brass to try and headspace off the shoulder. Besides, i'm not sure that is a good idea for first firings of new brass anyhow....

So I headspaced off the belt, with about .002" excess. This is less than the SAAMI specs show in variation for the 7RM, so I think its OK. 2 layers of scotch tape will not close. One closes reluctantly. Zero closes like butter.

Here's the question: I typically load virgin rimless brass with a bullet seated into the rifling. This assures that the cartridge base is pushed back up against the bolt face. That in turn means that there will be little or no case body stretch and the shoulder will be blown forward. Thereafter, I neck size, with the occassional body bump back .002" if the brass is getting too hard to chamber.

Should I do the same thing with the belted magnum brass? Essentially attempt to make the belt superfluous? I plan to neck size my 7RM as well, treat it like any other brass that I keep the shoulder the same to avoid case stretch over time.....



Thanks in advance.......

[bigedp51]

Eventually you will need to bump the shoulder back so why not full length resize with minimum shoulder bump and still headspace of the case shoulder.

The make of case and its thickness just above the belt may cause you problems. The case may bulge above the belt and the die may not size the case enough just above the belt.

If the case does bulge it can cause the case to bind in the chamber and hard bolt lift. Larry Willis makes a belted magnum collet resizing die the will size the case just above the belt.

http://www.larrywillis.com/

[cdherman]

I am aware of Larry's sizing die. Might be needed down the road.

I am mostly debating how to maximize my Norma brass longevity. Would like to avoid Larry's die, but I think its in my future. Norma brass, though consistent and well thought of, is rumored to be on the soft side.

[yobuck]

If your plan is to use the gun for hunting with something like 3000 fps in mind, then do yourself a favor and full length resize.
The primer pocket will go first, regardless of how you size.
Run every round thru the gun before you take them hunting.

[wbm]

If your plan is to use the gun for hunting with something like 3000 fps in mind, then do yourself a favor and full length resize.
The primer pocket will go first, regardless of how you size.
Run every round thru the gun before you take them hunting.

Ditto!