The AR 15 continues to prove its versatility in all kinds of ways - even ways that leave you scratching your head and asking "why?" For instance, I heard about the AR 15 muzzleloader upper at SHOT and looked in vain for it, finally concluding that it was a Mythical Creature and not a real AR accessory. Since then, I have found these two videos that prove its existence.
And, to give the people at CMMG Inc. credit, the .50 upper is cleverly designed. As you see in the video, the magazine holds extra pellets and bullets for handy reloading, and the gun will handle a three-pellet (150 gr.) load of pyrodex.
Besides the complete lack of traditionality, I don't have any problem with this, except that you would have to explain why you were carrying an AR 15 during muzzleloader season to any game warden who happened to spot you.