from what i have read and my experiences with AR rifles, the big .308s are many times over gassed. with an adjustable gas block i can fine tune for a wider variety of loads. some commercial loads are on the hot end of the spectrum and could possibly cause problems in an autoloader. adjustable gas block would just give a wider range of choices. i like plenty of choices. and that is one of the fun things about AR rifles, they are like legos. i liked legos. <thumbsup> liontribe