Ho-401 was a Japanese aircraft autocannon that saw limited, if any, use during World War II. It was a large-caliber version of the 37 mm Ho-203 cannon. The cannon was used on the ground-attack, Kawasaki Ki-102b heavy fighter of the Imperial Japanese Army Air Force.^[1]

• Caliber: 57 mm (2.25 in)
• Ammunition: 57 x 121R (1,550 g)
• Weight: 150 kg (330 lb)
• Rate of fire: 80 rounds/min
• Muzzle velocity: 495 m/s (1,624 ft/s)

• Gustin, Emmanuel; Williams, Anthony G. (2003). Flying Guns: The Development of Aircraft Guns, Ammunition and Installations 1933–1945. Marlborough, UK: Airlife. ISBN 978-1-84037-227-4.

• The Pacific War Encyclopedia