Rather than send everyone to the other link I figured I would post my last response here. My upper has been sent back and forth to BCM 3 times now for the same issue (weird wear on the gas tube). BCM has been great about taking it back and looking over everything. To this point, the have replaced the gas tube three times, Replaced the upper, replaced the gas key and supposedly replaced the bolt carrier on the last trip. They also provided a new charging handle as they feel even thought wear on the gas tube is completely normal that this is the cause of this excessive wear.
I received my upper back this evening and upon inspection (with the new charging handle in place) the wear is again on the new gas tube (same spot).
At this point there isn't much I can see them doing different. Again they have taken the upper back multiple times and worked over everything. Unfortunately I am just not happy with the fact that this is continuing to happen. I understand that I may very well be blowing this out of proportion and that this wear could be/is normal. I just have never seen it on any of my other uppers (including BCM's). So I am NOT going to send it back to them at this point. Will just see what happens.