Well, I took my M1A out for some weekday trigger time.  I decided to do a little ammo test and compare Portugese, Spanish Santa Barbara, and plain old Winchester .308.

Unfortunately, when I came home and cleaned the rifle, I noticed what looks like some damage.  Just left of the circle at the end of the oprod slide you can see there's a small nick in the reciever.  I realize the pic sucks, but you can still see what I'm referring to.  Its only a shallow dip, but I'd like to keep it from getting worse.

I'm wondering if maybe some of the ammo I shot was a little too hot that it sent the oprod a little further back than it should have went?  I don't know if that's even possible, but I'm at a loss as it to where the damage came from.  Any thoughts?

I can't see anything abnormal from the picture, but it is hard to see that section clearly from it.
The machined groove cut at the bottom left of the circle at the rear of the op rod track on the receiver is what's suppose to be there and is the same on mine. If there is something more than can be seen from the pic than who knows, but there is going to finish and metal wear in various places as the rifle breaks in. Unless an actual part of the metal of the receiver or the op rod chips off, I wouldn't worry about it.

Yeah, the pic does suck.

The groove to the bottom left of the circle is what I'm referring to.  Its quite shallow and looks too smooth to be something that would be caused by accident.  I guess I just never noticed it before....erm...  Thanks for the reply though.   I guess if all is normal, the mods can lock this thread up.

there is supposed to be a small groove back there, the pic makes it hard to see if there's anything abnormal though.

If you are concerned about it, you can get a buffer that will help dampen the movement of the oprod and recoil pulse.  Some like them, some don't.

http://www.buffertech.com/stores/1/index.cfm

I've got them on my rifles, but I don't think it's important too.

That groove is the same on my new M1A. I've got 300 rounds through her so far, but it was there from the beginning. No worries...

It's not likely that your op rod is gouging your receiver. The surface hardness of your receiver should be quite a bit harder that your op rod.