Weird marking on fired brass

Just finished my first build. 110 action, 26" Shilen select match in 260 remington. Headspaced with Forster go and no go gauge. Bolt stops about a third of the way down on the no go gauge. Fired a few Federal rounds with a 140 sierra game king to start break in. I noticed the concentric rings on the shoulder of the case, and it just looks kind of funny. Nothing else out of the way, is this anything to be worried about? It almost looks like there was a burr on the reamer for my barrel.

http://farm9.staticflickr.com/8192/8...9587d01d85.jpg
2012-10-25_21-26-21_734 by bsshep1, on Flickr