This is AR Technical discussion. Blanket statements such as "loctite will burn off" or "just buy a BCM" are worthless and add nothing to the conversation.
Bill from Alexander Arms use(d?) Loctite 243. I find it interesting he decided to use a thread locker. Loctite 609 looks interesting, especially since its labeled as "Recommended for parts that will need subsequent dismantling, i.e., retention of bearings onto shafts and into housings." My guess is a retaining compound wasn't chosen as, obviously, we are using a barrel nut.
I read somewhere else people use similar compounds on the barrel between the gas block. If anyone has any insight on this i'd love to hear about it.

