The AR-15 is one of the most successful rifles in history, both for the military and civilians. The only thing that could make the AR-15 better is bigger rounds, specifically 7.62 mm rounds instead of the standard 5.56 mm.
Eugene Stoner's original design of the AR-10, which is the predecessor of the AR-15, used 7.62 mm rounds. These rounds were the military designation for the .308 cartridges. The drive to create larger caliber AR rifles came from two different directions. The first from hunters, who needed bigger rounds to hunt big game. Second, from the military, which was responding to the necessity of longer shots in battlefields, such as the mountain ranges in Afghanistan.
Companies such as Remington and tactically-oriented Daniel Defense, offer larger caliber ARs designed for the hunter. As a result, the AR is the fastest growing hunting rifle in America. Eugene Stoner would be proud to see how far his platform has come. One thing is for certain, the big bore ARs are here to stay.