Instructions for Mounting the carbon fiber hand guard, any length
Remove the small screws on the outside of the back end. The number varies from 4 to 6 depending on the length.
Slip the rear mounting assemble out of the carbon fiber tube.
Remove the 4 screws holding down the U shaped plate.
Slip the GI barrel nut into the body of the rear mounting assembly, the gear shaped end will be right under where the U plate was mounted
Screw the barrel nut onto the upper receiver, tighten down to proper torque spec and align a notch in the barrel nut with the gas tube hole in the upper receiver.
Turn the body of the rear mounting assembly so that the gas tube hole is matching the hole and the barrel nut. You will be sliding the gas tube through all three holes, so they must line up.
Put the U plate back onto the rear mounting assembly, with the open end towards the top. Start each screw a couple of threads until all four are in place.
Tighten the screws, alternating back and forth, a turn or so on each at a time. As these screws continue to be tightened, this will cause the rear mounting assemble to draw into the barrel nut. There is a small tab on the very bottom of the rear mounting assembly that will draw into the bottom of the barrel nut in the notch that will be at the bottom center. There will be a little resistance as it tightens, this is normal, and is from the tab being drawn into the notch of the barrel nut. That tightness helps to keep it solid and not move when finished.
Alternating the tightening on the screws, go until the U plate is down against the rear mounting assembly flush. Make each screw tight to finish.
Mount your gas tube and gas block in place and tighten the mounting screws on the bottom of the gas block.
Slide the carbon rail onto the now mounted rear mounting assembly
Replace the outer screws and tighten.