Kernel Krink- Your post confirmed my suspicions. Iíll probably try and find a barrel and take measurements off of it, just for peace of mind. Thanks for the heads up.
Mad-Machinist- Thanks for the gas port info, this will come in handy when finding the proper placement for it. I plan on drawing up prints for the front sight base and moving it onto the barrel to find itís position. I figure the gas portís top dead center is dependent on the fitment of the barrel extension to the barrel, or are the threads timed on the barrel? If there not, why do you have to fit the front sight base yourself? Bushmaster will not sell barrels without this already installed, from what I read in their downloadable catalog. Iím not trying to make Stone Soup from asking a lot of questions, if you remember the old fairy-tail. I just want to be as accurate as possible and hope to benefit others who maybe wondering the same thing.