With the failure of the G30M and G30R to lead to any military orders (American or otherwise), the Winchester company took the advice of the Ordnance Department to scale the design up to an automatic rifle. The BAR had a number of known shortcomings in WWII, and the military was interested in replacing it. The Winchester Automatic Rifle (WAR) offered the same basic set of features with a lighter weight and lower cost.

The WAR used a 2-lug rotating bolt like the Garand's, in combination with a Williams short stroke gas tappet action. Chambered for the standard .30-06 cartridge and using 20-round magazines, the WAR could be used as a semiautomatic rifle or in full automatic with a rate of fire of approximately 600 rpm (slightly more or less depending on whether a muzzle device was used).

The WAR passed initial Ordnance inspection with flying colors, and a contract for 10 was placed, for more extensive testing. It passed these tests well, but they took place in the summer of 1945. By the time a major contract was a real possibility, World War II had ended, and the budget for new arms development was slashed. Had the war continued, the WAR likely would have begun to replace the BAR in US military service.