Depends where the head is contacting the receiver. I ASSume in the front, near where the lugs lock-up? on the top, or the bottom?
It can be fairly common to have it strike the upper part of the receiver, due to feed lips interfering with the bolt.
Either tweek them, or just time and some wear; also said a *LITTLE* bevel with a file can help. Just don't get crazy with the cheesewhiz on your receiver and a file.
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