Regarding feeding issues- Sometimes you can have trouble if the springs in the mags you are using are not broken in yet. Also with the Radway Green, I have a friend who experienced trouble using that in his FS2K. I have not shot it in mine yet. I did shoot the some of the rounds that were from his batch of Radway Green in an AR and there were no problems. -That said, I have heard that the Radway Green surplus 5.56 ammo that is on the market is a bit underpowered and that is why it can cause trouble.