Jim:
I'm not sure if your kit is the same as the US Army M-261 kit. It also uses 10 rd inserts into full sized mags. I have been playing with one for months. The problems I experienced were along the lines of failure to feed and eject properly. the FTF part was easily solved, no hollow points, and good mags. I found that the 10 rounders Bushmaster sells for their bullpup ( steel mags ) worked best. The insert needs to fit with as little play as possible. It also just didn't like any hollowpoint I ever tried either. On the ejecting side I would get empties caught between the bolt and charging handle. This I solved by very lightly stoning the ejector giving it a minute downward bevel. This combinded with using only Break Free CLP as a lube and the problems are greatly reduced. I went through about 150 rounds last week with only 2 malfunctions and that isn't bad for any semi auto .22