Originally Posted by oidg
I recently had a reputable gunsmith (that I'd rather not call out at this time) rebarrel a 7stw for me. I had shot out the previous barrel. The rebarreled rifle shot decent, about .75 MOA at the range today, but I expect it to shoot much better, as it was a sub 1/2 moa gun prior built on a stiller action. After getting home from my first trip to the range with it, I got out the Hornady headspace gauge. Growth from new unfired brass to once fired measured .020. I'd like some feedback from you guys before I bring this up with the smith. What is acceptable headspace growth? thanks
It is a different chamber and reamer that is the difference.
Head space is usually from .0005 to .003.
Two belted chambers with the same head space can produce two different length cases because they head space on the belt.
Once you fire form they should not change any more unless you have the dies set incorrectly
or you are over loading the case/cartridge.
The SAMME dimensions for a 7mm STW case length are 2.830 to 2.850.
So once you fire form the brass in you new chamber it should not change (You will have to reset your dies).
So if the chamber is .020 longer it is still within SAMME specs.
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