Nickel plated brass.

I was able to purchase 100 rounds of once fired Winchester Nickle plated brass for my 7mm Rem Mag. When I try to full length size I could not get the bolt to close, the head space is wrong so I put a .016 shim between the shell holder and the the brass and was able to bump the shoulder back enough to close the bolt. Read some place that nickel plated brass will spring back after sizing. Any one have any thoughts on this?
The plate would not affect the reflex. My thought is your die setting were not bumping the shoulder of brass from your rifle.
 
Sounds like a chamber differences. Just keep doing what you're doing as suggested. I haven't had any issues with the nickel brass I have. I wish I could get it in more calibers. I like it for hunting, it's usually easier to find on the ground.
 
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