Type 89 grenade discharger

Type 89 Grenade Discharger
Type 89 Grenade Discharger with various grenades, shells, and accessories
Type	Grenade launcher
Place of origin	Empire of Japan
Service history
In service	1929–1945 (Japan)
Used by	Imperial Japanese Army Indonesian National Army
Wars	Soviet–Japanese border conflicts, Second Sino-Japanese War, World War II Indonesian National Revolution
Specifications
Weight	4.7 kg (10 lb 6 oz)
Length	610 mm (24 in)
Barrel length	254 mm (10 in)
Cartridge	793 g (28 oz)
Caliber	50 mm (1.97 in)
Rate of fire	25 rpm
Effective firing range	(Type 89 shell): 120 m (131 yd)
Maximum firing range	(Type 89 shell): 670 m (732 yd)

The Type 89 Grenade Discharger (八九式重擲弾筒, Hachikyū-shiki jū-tekidantō^?), inaccurately and colloquially known as a knee mortar by Allied forces, is a Japanese grenade launcher or light mortar that was widely used in the Pacific Ocean theatre of World War II.

The Japanese Army, noting that grenades were short-ranged weapons, began efforts to optimize these weapons for close-in infantry fighting. After studying employment of grenades and mortars on the battlefield, the Japanese Army developed hand grenades, rifle grenades, and grenade/mortar shell dischargers (small mortars) suited to warfare in typical short-range combat environments such as urban, trench, and jungle warfare.

As part of this effort, the Japanese Army had adopted by 1932 a set of fragmentation grenades with almost universal adaptability. The Type 91 fragmentation grenade could be thrown by hand, fired from a spigot-type launcher, or used in a mortar-like grenade discharger, the Type 89.

The Type 89 Heavy Grenade Discharger was adopted in 1929, however production did not begin until 1932. It differs from the earlier Type 10 grenade discharger in that it has a rifled barrel. The Type 89 could fire two types of grenades or shells: the Type 91 Grenade, which was a normal infantry fragmentation grenade adapted to the Type 89 discharger, and the Type 89 50 mm shell, which was an impact-detonated shell with considerably more explosive power.

When fired from the Type 89 discharger, the Type 91 fragmentation grenade was fitted with a propellant base and time fuse. It did not explode upon contact, but was designed to ignite its fuse while in flight. A weak creep spring inside the grenade firing mechanism allowed the firing pin to be thrown back upon launching, igniting a time fuse with a 7-8 second delay. Using this system, the Type 91 grenades could be launched through jungle cover or through small openings without the danger of premature detonation in the event the grenade struck an object on its way to the target. Although the Type 89 could be fired by a single person, it was typically operated with a crew of 3, enabling it to reach a rate of fire of about 25 rounds per minute.