Just picked up my Smith & Wesson M&P10 in of course .308 Winchester that I had ordered. I had read about problems with the barrel and one claimed that his barrels split, said S&W would not help him and of course he had no pictures of it. Another mentioned that his barrel was stamped ".308 1/10 5R" so hard that you could see it in the barrel rifling opposite the stamp. Yep you can, see attached picture.
Hard to get a picture, either the bright light blured everything out, or the focus was off, but I did get one with enough light and in focus that you can see the high spots in the grooves of the rifling at the top, opposite the stamp on the outside of the barrel. In the picture you can only see a couple high spots, but there are several, again, just could not get the bright light and camera to get along. Some of the rifling looks poor also, don't think so, I have not cleaned the rifle at all and it looks like there is a preservative in the bore. S&W did not seem surprised when I called them about it, they already sent me a return label by e-mail and they said they would rebarrel if needed.