Would this upper work http://www.bravocompanyusa.com/BCM-Upper-Receiver-Groups-with-KeyMod-KMR-s/174.htm to replace a hbar upper I have on a post oct 1 rifle I have. it is marked nm on barrel witch I thinks stands for national match but in the description it say medium contour but looks .750 or greater the whole length of barrel. Thanks for help in advanced.