 ArmaLite and Winchester Arms were solicited by CONARC to provide prototype automatic rifles chambered for high-velocity centerfire .22 rounds.The ArmaLite AR-15 was a scaled-down version of the 7.62mm AR-10, which had appeared too late to be a serious contender against the M14 for adoption by the US Army.Its competitor was the Winchester .224 Light Rifle, a "Carbine" Williams prototype carbine design in a .22 high velocity round which was similar to, but not interchangeable with, the .223 Remington (5.56×45mm).