The Winchester 7mm RM brass I load does not thin at the web as fast as the R-P Remington brass.

Is new Winchester brass longer from the base of the case to it's shoulder? The handbook dimension is 2.040". The new WW brass I have measures 2.050"!

Even if fired brass is FL sized, like I do, so that it fits the specific rifles chamber so you can feel it when you close the bolt on a FL sized case the WW brass I have lasts much longer than R-P.

Can anyone measure an unfired new R-P 7mm Rem. Mag. case for me?

Full length sized to fit the chamber ?
I think you have your terms and/or method confused.
If you are full length resizing, your brass will be sized to your die, not the chamber that fired the round.
Also, FL sizing will reduce your case life (thinning at the web) due to stretching.

When I full length size a bottlenecked case like the 7mm RM the 'headspace' of the case or the distance from it's base to shoulder gets longer in the die as it constricts the sides of the case.

If I do not push the shoulder back much the bolt may not even close on that case until it is pushed back some by the FL die.

I test a case by FL sizing it a little bit more each try in the specific rifle. I put the three position safety on the middle position where it holds the firing pin back. That way you can feel the case in the chamber when closing the bolt carefully.

Some may call this partial full length sizing. I call it perfect full length sizing.

It's particularly valuable on belted bottlenecked cartridges.

If the new brass starts out short in it's 'headspace' then it will thin some at the web on its first firing. That's what I am concerned about on the Rem. brass.

I only have FL dies for the (6) belted mags I reload.
IF you are loading for (1) gun, try neck sizing only. Set your die up so the case head spaces on the shoulder (just like a non belted case). After a few loads you may have to 'Bump' the shoulder, but not every time. Your cases should stretch less and last longer and probably be more accurate.

I stopped neck sizing 50 years ago for hunting rifles.

I perfect FL size all.

I get around five out of my 300 win mag. I only use it for hunting elk when not using my 338.

I have a few hundred cases so 5 is not a problem for hunting ad zero checking.

So I full length resize If it was a shot a lot rifle I would try something different to get more reloading out of a case.

But just for hunting a few hundred cases is a few life times worth.

quote:

Some may call this partial full length sizing

I think calling this FL resizing caused the confusion.

As you said I reload all my belted magnums to headspace on the shoulder. I've found that even doing that I get a shorter life than a normal non belted. First load head spaced on the belt, long shoulder jump, heavier charges who knows. A 5-6 reload life would be fine.

quote:

As you said I reload all my belted magnums to headspace on the shoulder. I've found that even doing that I get a shorter life than a normal non belted.

I agree, thats what I find as well.

The reason is that the length to shoulder distance on belted cartridges with shoulders is that the case is made short in that dimension and the headpace fit is to the cartridge's belt and chamber.

It's a design 'defect' or conundrum that such belted rounds with shoulders have.

Just look at the cartridge and chamber drawings and their design tolerances and you will see that.

Thus when I fire a new 300 Win Mag in my chamber it headspaces in the chamber on the belt and blows the shoulder forward. That's why they thin at the web sooner than say the 30-06 and don't last as long!