I've had my Carbon 15 in "long term" storage at my dads until I was able to bring it to me, it wasn't sitting (in a dry and cool area) for more than 6 months. I recently got it back and was taking it apart to make sure everything was good and to re-oil it and I found this. This is with the upper upside down and looking into the charging handle groove near the stock side. It looks as if the composite is chipping off and exposing metal underneath. First off I work with composite material and it should actually be very difficult for something like this to happen, I've never seen it. Secondly there is bare metal underneath that appears to have a bit of rust on it. I've contacted Bushmaster and they are sending a label and I'll be shipping it to them and they will be evaluating whether it's natural wear and tear or a defect of the product. If it is found to be natural wear and tear it's very disappointing since there are less than 300 rounds through this rifle and I would have expected it to hold up better. Worst case I'll just have to buy a new upper receiver, maybe a new complete upper, but at that price I might as well buy a new AR. But as for now, I'll be without my AR for several weeks, minimum.