its easy. i put the DPMS 4 Picatinny rail on mine. i like the fact that i can fold the front sight down out of the way of the optic.
unload and make safe.
take the upper off the lower and remove the BCG/CH
remove the flash suppressor/muzzle brake and washer.
lighty lube the barrel to avoid scratching it when you slide the FSB off and your whatever on (i used the DPMS four rail gas block)
pop out the tiny roll pin that holds the gas tube into the FSB.
lighlty tap out the taper pins with a hammer and punch. sometimes it may take more than "light" taps. just be careful you don't scratch everything to heck.
slide the FSB off and your new gizmo on.
re-install the roll pin for the gas tube and align the gas holes. but Bobby, i can't see 'em! i know, grab a piece of 1/4" or 3/16" clear vinyl tubing, slip it over the gas tube in the receiver and blow while rotating/moving the new gas block around. where you get the least resistance is when the holes are aligned. leave it there and tighten the set screws.
re-install the washer and flash suppressor/muzzle break. install your front sight, go to the range and sight it in.
if you max out your rear sight adjustment, then your gas block is canted. loosen the set screws and rotate it in the appropriate direction and re-zero.
it seems more intimidating than it is. the hardest part about it is getting the top of the gas block level with the flat top.
Bobby
