I just got my 7mm rem mag back from the smith, where he trued the action and put on a new Mcgowen barrel. I loaded up some rounds in new Win brass and went to break in the new barrel. Upon firing I noticed the shoulders on my cases were blackened after firing. A few cases had six lines (from the six groove barrel) half way up the case body. At first I thought I wasn't getting the chamber dry after cleaning, but that wasn't it. After I fired all 21 rounds with many cleanings I had 21 cases all with black necks and shoulders. 5 or so had the lines up the case body. So I got home and measured up some cases with my headspace gauge. It wasn't too far off (.009 shorter) than my old fired rounds so I figured my head space was probably OK. I set up my fl die to bump the shoulders .001. This time I loaded up incremental charges to start load development. I thought maybe my break in rounds were a little under pressure in this rifle. All fired cases showed pretty much the same results as the new brass. Obviously I may need to talk to the smith that built this rifle but I thought I would run it by some of you guys first. I am very happy with the accuracy and the velocity of the rifle so far but I wonder if I am causing damage to my chamber or any thing else?