Japanese Type 100 Submachine gun

The Japanese were surprisingly late to design a submachine gun, an oddity considering the length of their conflict with the Chinese prior to 1941 and the number of different submachine gun designs brought into Japan for examination and study. It was not until 1942 that the first example of what had been a low-priority development left the Nambu production lines in the form of the Type 100, a sound but unremarkable weapon that was to be the only submachine gun the Japanese produced in any number.

The Type 100 was moderately well made but had several odd features. One was the use of a complex ammunition feed device that ensured the round was fully chambered before the firing pin would operate. The exact purpose of this feature is unknown (other than the safety aspect for the operator). The cartridge used by the Type 100 was the underpowered 8 mm Japanese pistol round, a rather weak and ineffective choice that was not aided by its bottle shape which added to the feed problem. The weapon’s barrel was chrome plated to aid in cleaning and to reduce wear. To add to such niceties, the design had a complex system of sights and a curved magazine that stuck out of the left side of the weapon. Also some versions had a complicated muzzle brake and a large bayonet mounting lug under the barrel, some even sported a bipod.

There were three versions of the Type 100, the first being described above. The second had a folding stock for use by paratroopers: the stock was hinged just behind the gun body allowing the stock to fold along side of the main weapon. Handy for carrying when parachuting, it weakened the weapon in combat situations and relatively few were produced.

The third version of the Type 100 appeared in 1944 at a time when demands for submachine guns were coming from all fronts. In order to expedite production the Type 100 was greatly simplified and in the process the design was lengthened slightly. The wooden stock was left with a rough finish and the rate of fire increased from 450 rpm to 800 rpm. The sights were reduced to little more than aiming posts and the large bayonet lug was replaced with a simpler mounting. At the muzzle, the barrel protruded from the perforated jacketing and the muzzle brake was replaced with two vents drilled in the top of the muzzle. Welding, often rough, was used whenever possible. The result was a much cruder weapon than the early Type 100s, but one sound enough for it’s purpose.

The main problem for the Japanese by 1944 was not so much that they Type 100 was not good enough but the capacity to turn out the huge numbers needed. Consequently the Japanese had to fight their last-ditch defense at a permanent disadvantage against the better equipped Allied forces.

As a whole all of Japan's arms were inferrior and outdated. The lack of a semi-automatic rifle also hurt. The Type 100 was designed to fill the same role as the American Thompson and "Greese gun." Unfortunatly due to production and complications combined with the allied bombing of factories the Type 100 could not be produced in great quantities. For most of the war only the most elite units of the Japanese army were equiped with the Type 100. By the time the regualar army started recieving the Type 100, the quality had deterriorated, at times the weapon's assembly included nails. What few attributes the Type 100 had it quickly lost as quality declined.

Specifications

Sources: specifications and other bits from The Encyclopedia of Weapons of World War II; much is from memory

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