I noticed that a wear area is forming on my 870 Express' receiver. It is on the underside of the top of the receiver about dead smack in the middle both side to side and front to back. I believe it is being caused by what Remington calls the "lock block assembly" or as I have always heard it called, the bolt, when the bolt travels backwards. There is a long rub mark (not deep or sharp) that ends in a rounded 'lump' where a small amount of metal is being displaced. The 'lump' and resulting depression is very small, maybe 1/8" x 1/8" and 1/16" deep at most. Obviously the reciever is being smacked by the bolt at it's most rearward travel. Short of smoking parts of the top of the bolt and trying to figure out what is making the contact I'll just have to say it's somewhere on top of the bolt. This could be a normal occurance with Rem shotguns, I really don't know. It however does not look normal. As this is my first experience with an 870 (mostly have shot/used Moss 500's) is this a normal occurance after 250-300 shots (mostly 2/12" and a few 3" shells)? I'd rather not tie up my favorite shotgun at a gunsmith for weeks on end if this is a non issue.