Since the expiration of the AWB, I wanted to know about replacing the fake flash hider on my RRA M4 barrel.  I don't care about a bayonet lug since it is a 16" barrel, but I would like a real flash hider and not have to replace the whole barrel.

Yes you can. You have two options. The first is to press off the fake flash hider and thread the barrel. The advantages of this option are that the flash hider does not have to be permanently attached and you retain the velocity of a 16" barrel. The disadvantage is that the you are left with a fugly contour.  The second option is to chop the barrel, thread it, and permaently attach the muzzle device of your choice (usually Phantom or Vortex, or an A1/A2 if they cut less of the barrel, but I'm not sure what the contour will look like). Adco can do either of the options.

I had them do the second option on my RRA barrel and permanently attach a Phantom:

Send the upper to ADCO and let them swap it out. I've always been very pleased with there work.

www.adcofirearms.com