TrueShot made it easy peasy for anyone wanting to go the M4 route or any non floating front end. The few of us that did it first had to have spacers machined or came up with something on our own!
All I can say is thanks to BELT_FED for machining the spacer to make my Armalite AR15 A2 sight post work! (this was before TrueShot had one)