I will say this and only this in Hesse's defense, there is one guy that owns one and posts on Biggerhammer. So far he has a few hundred rounds through his and hasn't had any problems yet.
Steve,
Watson's Weapon's makes the .50 upper for the AR that you have to screw the bolt in and out to load and unload it. The Ferret50, ALRS and the MMAG are all true bolt action types uppers for the AR lower.