The RIS is always a little loose on any M4 even real steel but, if it is to loose for your liking give us a photo showing how loose it is. Maybe there is a loose bolt or something we can help you with. (Sorry I don't know to much about M4's the MK16 is my gun of choice.)
I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.
US (German-born) physicist (1879 - 1955)