How much headspace?

[Alderman]

I've been measuring some unfired vs fired brass and finding the difference in length to the shoulder is .004.
Is this an expected and acceptable amount of stretching?

 

[Rol_P]

My Montana 30-06 shows about .003" increase in base to shoulder when looking at Nosler cases.

 

[SJB358]

That's fine by me. After that I'd never push them back more that .002 though.

 

[ElmerThud]

New unfired brass headspace dimension is largely irrelevant. Measure fired brass (from your rifle) after the primer has been de-capped:...say, measure ten & use the average headspace dimension as your baseline. Never bump back by more than .002" - that's where your F/L sizing die should be set in my view.
Different brass makes may easily show slightly different measurements depending on how far back the brass springs after firing.
Setting up this way is a great help in achieving consistency.