I have a 16" post ban RRA upper with muzzle break. I want to install a NM barrel. I have a couple questions. If I pull off the 16" is the barrel nut reusable? Seeing that it won't come off easy. What esle will I need beside barrel, gas tube and handguard. I'll be going with the RRA barrel. I've never done this before, but I'm very handy. It seems easy from some of the posts I've read. Thanks.