Its an extractor issue. I have a 700 that went for about 1500 rds before the stock extractor finally gave out, I never had a problem. I replaced it with another Facotry Rem. replacement and have had the same marks you have ever since.
I'm inclined to agree with the extractor opinion, but have two VERY BASIC questions first.
1. How long did you have the rifle before you noticed the marks beginning to build up?
2. Did you have any work done on the rifle before the marks began to mar the finish?
If the answer to number two is NO, and the answer to number one is almost immediately, You probably have a warranty issue that can be resolved by simply taking the rifle back to the seller/manufacturer for warranty work. If the answer to number two is yes, you need to talk to the person who last worked on the rifle (depending upon what work they did of course). Good luck.
This was Remington's response:"It is normal for the ejection path to sometimes cause the fired round to hit the gun. This really shouldn't cause any problems. We hope this information is helpful and we appreciate your loyal support of Remington products."
I have been shooting BDL's (hunting rifles) ever since I can remember and I would have to call bull....... (you know) on that. Even in the heat of trying to hurry for a second shot on animals my brass has never came back and hit the rifle like that. Just $.02 though.
Yeah, That doesnt seem like a "normal" thing and if it is they need to be sued for selling a faultly product. Id take it to a qualified gunsmith and have him check it out to see what the problem is. If the gunsmith says its a bad extractor id send it back and try to get my money back and buy from a diffrent company.
While it is not normal, it can happen. I fixed mine after reading this post. Its simple to fix, tear your bolt down and trim a coil off of the Ejector spring. I just trimmed about a half coil then tried it out, it wasn't enough so I went a little more. It is perfect now. Hope this helps.