Has anyone tried or know if the .50 caliber Beowulf upper will fit on the M&P 15 lower? The description on Cabela's says it's for the Colt AR-15 but wondered if there was anything "special" about the Colt vs. other manufacturer's "mil-spec" ARs. I'm new to the platform but am enjoying playing with it and replacing some components to improve the feel and function of the gun. It seems to me that running a .50 cal would require a change in the recoil buffer, but I'm sure it'll still be a heck of a recoil in any case (firing a 334 grain bullet has got be harsher than a 55 grain). Thanks in advance for any comments.