That is a DPMS upper. FYI, when I contacted Brownells to order extra 10 round mags, they had 8 left. So, if you go with the upper and want more mags, order them at the same time. DPMS has no 10 round mags. Per customer service, they are going to be making more of them in the next month or so. Midway USA has them backordered until the middle of May. No word on the 25 round hi-caps, again per DPMS they are re-tooling, and have no eta on the release date, just later this year.
When I was talking to Dustin at the gun show, he told me that they are currently not making the .22 uppers because they are redesigning the way the bolt assembly locks onto the chamber. Currently it just slides over the chamber. Apparantly (I've not had it happen to me) if the chamber gets very dirty, you can have an out of battery firing. According to Dustin that will blow off an extractor (there are 2 of them on the bolt), and possibly blow the mag out of the mag well. I have read of people having those problems. I told him that after I am done shooting I scrub the chamber with a barrel brush, and he told me that I should have no problems with the out of battery firing. I have got 1222 rounds through mine (I thought it would have been more), and have had no problems. I wanted to pick up one of thier M-4 uppers in Pre-ban configuration so I could have a nice scoped upper.
I have their DCM upper in Pre-ban configuration, and I really like it. I would recomend it.
Good luck sir!
Brad