The Ho-301 was a Japanese 40 millimeter

caliber In guns, particularly firearms, caliber (or calibre; sometimes abbreviated as "cal") is the specified nominal internal diameter of the gun barrel Gauge (firearms) , bore – regardless of how or where the bore is measured and whether the f ...

autocannon An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber ( or more) armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bull ...

that saw limited use during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, on Japanese Army

Nakajima Ki-44 The Nakajima Ki-44 ''Shoki'' (鍾馗, " Devil Queller") was a single-seat fighter-interceptor which was developed by the Nakajima Aircraft Company and operated by the Imperial Japanese Army from 1942 to 1945 during World War II. Its official de ...

and

Kawasaki Ki-45 The Kawasaki Ki-45 ''Toryu'' (屠龍, "Dragonslayer") was a two-seat, twin-engine heavy fighter used by the Imperial Japanese Army in World War II. The army gave it the designation "Type 2 Two-Seat Fighter"; the Allied reporting name was "Nick". ...

KAI aircraft. It was unusual in using caseless ammunition. Although the effective range of the cannon was only 150 meters (490 ft), the Ho-301 was light and rapid-firing for its caliber. The caseless design revolved around a specially designed projectile, that was in effect a small rocket. The round used an internal propellant chamber at the rear of the projectile containing a ten gram silk bag filled with smokeless powder. Drilled into the base plate of the round are twelve 3.8 millimeter diameter exhaust holes. The propellant chamber is sealed by a thin aluminum sealing cup, which covers the exhaust holes. When the primer is struck, the bag of propellant ignites, and the pressure rises until the aluminum cup bursts, allowing the exhaust gas to rush through the exhaust holes pushing the projectile forward. The propellant was exhausted before the projectile left the barrel. Because of the low muzzle velocity (245 meters/second or about 804 ft/sec - equivalent to a moderately powerful

air rifle An air gun or airgun is a gun that fires projectiles pneumatically with compressed air or other gases that are mechanically pressurized ''without'' involving any chemical reactions, in contrast to a firearm, which pressurizes gases ''chem ...

) the weapon was only suited to attacking bombers; even here the extremely low muzzle velocity made it difficult to achieve hits from any position besides directly astern the target aircraft and well within the range of defensive counterfire. The modern Russian VOG grenades fired by the

GP-25 The GP-25 ''Kostyor'' ("Bonfire"), GP-30 ''Obuvka'' ("Footwear") and GP-34 are a family of Russian 40 mm under-barrel grenade launchers (''Granatomyot Podstvolnyj'') for the AK family of assault rifles. They were first seen by the West in ...

grenade-launcher A grenade launcher is a weapon that fires a specially-designed large-caliber projectile, often with an explosive, Smoke screen, smoke or tear gas, gas warhead. Today, the term generally refers to a class of dedicated firearms firing unitary grena ...

use a similar principle.

Ammunition specifications

* Length of projectile (fuzed): 129 mm * Diameter of rotating band: 41 mm * Diameter of body: 39 mm * Wall thickness: 4 mm - 5 mm * Weight: 0.590 kg * Explosive content: 0.065 kg approx TM gives content as 2 ounces of H.E. filling plus 0.1 ounces of primer and 0.2 ounce gaine. * Fuze: Direct acting impact fuze

References

* * 40 mm artillery Aircraft guns Autocannon Machine guns of Japan Caseless firearms Military equipment introduced from 1940 to 1944 {{Machinegun-stub

Ammunition specifications

See also

References