heat gun worked for me as well, but like others have said...I had to crank it ALL the way up. Also make sure you strip the gun completely (including taking off the buttstock). The recoil buffer actually makes a nice handle why you are toasting it like a hotdog. ha On my M4 benelli had put so much loctite on it that I had to keep applying as I turned the tube. Eventually I did get it off. A technique that worked for me was to place the receiver between your knees and then twist hard w/ your hands.
Good luck and happy roasting!