I just purchased a new DPMS DCM upper from one of your vendors and took to the range for the first time today. I have three other complete DPMS rifles which none have ever had a single malfunction. I cleaned, lubed, and prepped this upper just like I have all the others, and put onto one of the three lowers. During the 20 shot break-in, shoot once and clean, the bolt would not stay open on the empty mag as I loaded one-by-one. Upon finishing the 20 shots, I loaded five rounds into the mag and proceed to have a failure to feed on every shot. The bolt was denting the cartridge case and not taking it out of the mag fully. I came home, read the thread below, and tried polishing the chamber as suggested. When I headed back to the range, still no luck. The fired cartridge is ejecting ok, but not nearly as far as any of my other three DPMS rifles, maybe two to three feet and 3 o'clock instead of the normal six or seven feet at 5 o'clock. I tried five different magazines, not one would make a difference. I tried the ammo, Black Hills, in one of the other rifles, not one malfunction. I tried the new upper on one of the other lowers, same problem. I went ahead and fired another 50 rounds to see if it would break-in, no change. If I pull back the charging handle maunally, it will catch and will stay back until I use the bolt release. It then chambers fine and fires fine.
As I am not really a gunsmith, by any stretch, I guess I should be sending this right back to you for inspection/repair unless there is something simple I am missing... Suggestions will be appreciated. I have been very happy with all my rifles in the past, probably 8-10,000 rounds total with ZERO problems, and I just want to be sure I have another reliable toy!!
Edited to add the vendor has graciuosly agreed to an exchange, so I will be receiving a new upper next week. I would still like to hear what you think about this problem, so I am leaving the thread for now.