Another happy CMMG user here. Mine also doesn't like the Federal 525 pack ammo, at least 1 FTF/FTE/stovepipe every mag. It runs 100% with Winchester Dynapoint GT's and the 333/555 pack ammo.
Accuracy is so-so, about 3-4" at 50yds, but it is a ton of fun and good for cheap CQB practice and close range blasting. I got my kit and extra BDM mags from Questar and was happy with their price and service.
Mark