1962 Rifle, Automatic, Caliber .223, Armalite AR15, Colt Model SPAR 30-62.A.1
A circa-1962 layout from the U.S. Army’s Springfield Armory showing an early Colt 601. Note that the last 6 inches of its 20-inch barrel are past the forward sight assembly, with overall length hitting just shy of 39 inches.