Type 10 Grenade

Type 10 Grenade
A drawing of a Type 10 grenade
Type	Hand grenade/Rifle grenade
Place of origin	Empire of Japan
Service history
In service	1921–1945
Used by	Imperial Japanese Army  Imperial Japanese Navy
Wars	Second Sino-Japanese War Soviet-Japanese Border Wars World War II
Production history
Designed	1914
Specifications
Weight	530 grams
Length	125 mm (4.9 in)
Diameter	50 mm (2.0 in)
Filling	TNT
Filling weight	50 grams
Detonation mechanism	Pyrotechnic delay of 7 to 8 seconds.

The Type 10 Grenade (十年式手榴弾, Jyūnen-shiki Teryūdan) was the first fragmentation hand grenade designed and deployed by the Imperial Japanese Army.

After the Russo-Japanese War of 1904–1905, the Japanese army experimented with a variety of grenades; however, no design reached mass production. Japanese military observers in the European front of World War I noted the technical development and tactical application of hand grenades as infantry support weapons with considerable interest, and the Army Technical Bureau was tasked with a project to develop a grenade launcher that could be used in combination with the Type 38 rifle, the Japanese Army's standard infantry weapon. The project failed for a variety of reasons, including too small a bore, too long a gun barrel and difficulties with a propellant. The Technical Bureau then turned to a World War I-vintage German design for a small signal mortar, which was developed into the stand-alone Type 10 Grenade Discharger. The Type 10 grenade was designed for use with this grenade launcher when attached to a base containing a primer and propelling charge. It could also be thrown by hand, or fired from a rifle grenade launcher with a tail assembly added.

The design of the Type 10 grenade was almost identical to the later Type 91 with a grooved 'pineapple-shaped' segmented body designed to disperse sharp fragments when it exploded. The main difference was the Type 10's serrated top. A threaded socket in the bottom of the body allowed for the attachment of an auxiliary propellant canister for use in a grenade launcher, or a finned tail assembly for use as a rifle grenade. The fuse was a percussion-activated delay type, initiated by pulling out a safety pin and striking the top of the cap, which gave a 7–8 second delay. When used as a rifle grenade or mortar round, the fuse activated automatically, as the plunger was pushed in by the force of the launch. One issue with the design was the highly variable and inaccurate fuse timing, which resulted either in premature explosion, or such a long delay that the recipient could hurl the grenade back prior to detonation.