I'm confused. gibby29 says he put it on using lubrication. So presumably he knows if it has thread locker. I'd saturate it in penetrating oil like kroil for awhile. Then add heat. Lots as suggested. and make sure I have a setup to apply torque that is solid. That is always an issue when you don't have barrel lugs to use.
“So in war, the way is to avoid what is strong, and strike at what is weak.”
PB Blaster is good stuff. I had a RRA upper that I wanted a rail on but could not get the original nut off. I had a local gunsmith who said he would do it for $40.00. I came back a couple days later and he could not wait to get it out of his store. He never had a nut that was on so tight, that he had to use a torch and numerous other things to finally loosen it. It was the best $40.00 I ever spent. I don't know why some companies put them on the way they do.