Home Forums Reloading Big Game Rifles New 7mag brass, headspace issue??

So, bought a batch of Winchester new and primed brass for my 7 mag. I measured from the base to a midpoint on the shoulder with the stony point head space gauge and it’s .015-.020” shorter than my fired cases (to the same spot on the shoulder). Is this a big deal or not? Wasn’t sure if it is irrelevant since belted magnums “headspace off the belt” (or so, I have read).
What say you?
Can it be safely loaded?

And will there be much difference from a “near top end load” in the shorter case and the same load in the same case once it has been fired and expanded to chamber dimensions?

Fifteen to 20 thou is quite a bit. If you're concerned with maximum brass life, you can always neck them to 30 cal & size back down to 7mm leaving a 2ndary shoulder to hold the cartridge face against the bolt face. You will be headspacing off the shoulder this way.

Not sure if your comparator will measure the smaller diameter bump. It's done either by feel (snug bolt close) or already having your 7 mag die set up with fully formed brass. If you do it by feel keep the locking lugs lubed.

Since it's a new & different lot of brass why would you start with a “near top end load”? The "rule" when I was learning was 10% reduction when changing anything. A 5% reduction is usually enough. Do as you wish.

It's normal, it headspaces off the belt. You'll get a lot of stretch on the first firing so reloading it you'll need to use the shoulder to headspace it.