Done a LOT of searching on the web and can't find an answer. I wanna buy a YHM gas block with flip-up sight since I"ll be springing for an optic soon. The YHM gas block has a .750 bore diameter for the gas tube. Is this the standard size gas tube for all carbine-length ARs? Specifically my 6920. I just don't wanna go through the hassle of ordering an expensive part to get it home and find out its the wrong size. Thanks in advance.