The Ho-103 (12.7mm Type 1) was a Japanese aircraft machine gun widely used during World War II and also known as the Ho-104. The Ho-103 was actually a fixed gun and the Ho-104 a flexible gun. It was based on the American .50 BMG M1921 aircraft Browning machine gun but with a higher ROF using a smaller, lower velocity Breda (Vickers) cartridge, intermediate in length between German 13mm calibre MG131's 64mm length cartridge, and the long 99mm cartridge of the M2 Browning .50 calibre machine gun. Because of this, the weapon was frequently loaded with explosive or incendiary rounds to increase terminal effects on aircraft.