During World War I, Colt surpassed all previous production achievements. John Browning worked for Colt for a time, and came up with a design for a semiautomatic pistol, which debuted as the Colt M1900 pistol and eventually evolved into the M1911. Prior to America's entry into the war, orders from Canada and the United Kingdom swelled the backlog of orders to three years. Colt hired 4,000 more workers, making a total of 10,000 employees—and its stock's price increased by 400%. By 1918, Colt had produced and sold 425,500 of the famous Browning-designed M1911. Because the factory could not keep up with demand for this pistol, the US Military decided to accept Colt New Service revolvers in caliber .45 ACP, called the M1917 revolver, as a substitute weapon. Competing manufacturer Smith & Wesson made double-action revolvers in .45 ACP, which were accepted and issued by the U.S. military under the same name. Colt produced 151,700 revolvers during the war as well as 13,000 Maxim-Vickers machine guns and 10,000 Browning machine guns with an additional 100,000 under subcontract to other companies.