I don't see where you specified which weapon you are discussing. I highly recommend you click the link. Even the ATF, or what the ATF was in 1963, views them as two separate weapons. The citation also will tell when the Colt AR 15 was classified as a civilian weapon. It will also tell when the Colt AR 15 went on the market and when the M 16 was issued to the troops. If you read the citation you might ask yourself "if the Colt AR 15 was designed for the battlefield why was it sold to civilians BEFORE the M 16 was issued to troops why didn't they just issue the Colt AR 15?"
Game. Set. Match.