Before the United States entered World War II, Saginaw's industrial complex became directed towards military production. Turning its efforts to the production of munitions, ordnance and components for military vehicles made Saginaw a significant contributor to the Allies' victory. Saginaw was home to a production facility that produced .30 caliber machine guns more quickly and at lower cost than the Army thought possible, armor-piercing shells for anti-tank use, and more than half a million M1 carbine rifles for the US military during World War II, the "Gun Plant" that later became Steering Gear Plant 2. Saginaw Steering Gear's Plant1 also began wartime production in 1941, concentrating on ball screws that would eventually be used in the wing flaps of the Boeing B-29 Superfortress. Malleable Iron converted its production of Armasteel from engine components to gun parts and tank treads, while Grey Iron specialized in the production of magnesium for use in Pratt and Whitney aeroplane engines.