Ho-401 cannon

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	Weapon: Ho-401 cannon Type: Autocannon Country of Origin: Japan Year Adopted: Caliber: 57x121mmR Action: Short Recoil Overall Length (mm): 2000.0 Overall Length (in): 78.74 Weight (kg): 150.00 Weight (pounds): 330.69 Effective Range (m): 1200 m Effective Range (yards): 1312.34

The Ho-401 was a Japanese 57mm aircraft cannon developed during World War II by the Army Technical Bureau for use in ground-attack roles. Based on Japan's earlier experience with large-caliber aircraft weapons like the Ho-301 grenade launcher, the Ho-401 was designed to deliver a much more powerful explosive payload. It was a short-recoil operated, belt-fed cannon weighing approximately 150 kg and had a modest muzzle velocity of about 495 m/s. The cannon was chambered for a 57x121R cartridge, optimized for destructive effect rather than high velocity or armor penetration.

The Ho-401 was intended to arm heavy attack aircraft like the Kawasaki Ki-102, where it could be used for tank-busting or other ground support missions. However, the weapon was only produced in extremely limited numbers, likely fewer than a few dozen units, and never reached mass production. Its integration into aircraft was experimental, and it faced numerous technical and logistical challenges, such as excessive recoil, low rate of fire, and limited ammunition capacity (often no more than 16-20 rounds). These limitations, combined with Japan's deteriorating wartime industrial capacity, severely restricted its deployment.

In terms of service history, the Ho-401 saw little to no operational combat use before Japan's surrender in 1945. Its large caliber made it a rare and formidable design on paper, but it was ultimately impractical for the realities of aerial combat at the time. While never notorious due to its limited exposure, the Ho-401 remains a notable example of late-war Japanese attempts to match Allied air-to-ground firepower, and it stands as a unique weapon in the history of aviation armament. Today, it is primarily of interest to collectors and historians studying experimental Japanese aircraft weapons.