The M1921 Browning machine gun was a water-cooled .50-caliber (12.7 mm) machine gun, designed by John Moses Browning, which entered production in 1929. From 1917 to 1918, he developed the prototype Browning Winchester Cal.50 caliber heavy machine gun. It was developed from a water-cooled .30 caliber M1917 Browning machine gun.