Sounds like you have a good set of components working there. That Rainer rail is pretty good. I've one for my SBR build (tip from Edge). The barrel nut comes with it. And since you're using the rail, you don't need a delta ring.
I also got one of the raptor handles for the same SBR build. I'll tell you, I'm liking these handles alot. I also use one on my DD M4. They just kinda feel right, when you grab them. And smooth by the way.