The Japanese military of the Second World War is undoubtedly unique among the fighting countries of the conflict. One of the interesting peculiarities of the Japanese military is its use of submachineguns, or lack thereof. Essentially every major nation to take part in World War Two relied heavily on the use of sub machine guns. Many countries, like Germany formed a part of their infantry attack doctrine on the use of the Maschinenpistole 38 and 40 (MP 38/40). The Russians cranked out millions of PPSH 40’s and PPS 43’s to arm the Red Army. The United States had the venerable Thompson submachinegun, and the British were armed with the Sten gun. Even the Australians had the domestically produced Owen gun with which they fought the Japanese in the jungles of Burma to great effect.
Japanese servicement with MP34 (left) and the Swiss produced SIG Bergmann M1920 (right). Photo courtesy of Austin Adachi.
The Japanese were quite late in the game, only adopting the Type 100 submachinegun in 1940 and deliveries began in 1942. Before this time, the Japanese had imported limited quantities of the Swiss SIG Bergman M1920 and the German produced MP 34. These submachineguns were primarily used by the Japanese Navy and Naval infantry. Undoubtedly, these compact fully automatic firearms would have been easier to use on a vessel and provide a large amount of firepower to small naval landing parties. In the early 1930’s the Japanese ordnance department began experimenting with the idea of a domestically produced submachinegun. As the Japanese war machine advanced across southeast Asia they began to understand the impact that a small caliber, fully automatic weapon could have in the thick confines of a jungle environment. The Imperial Japanese Army also wanted a compact weapon that could provide large amounts of firepower for their airborne forces. Design work began at the Nambu Rifle Manufacturing Company. Several prototypes were tested, and changes were made throughout the testing process until a suitable weapon was developed.
Being formally adopted in 1940, the Type 100 took many elements from the Swiss and German weapons already in use with the Imperial Navy, such as the side mounted magazine, and ventilated barrel shroud. The Japanese also gave the weapon a bayonet lug and chambered the weapon in the domestic 8x22mm Nambu cartridge. Two major models of the Type 100 were produced, with an additional version of the first model having a folding buttstock and removeable barrel assembly for airborne use. The first model, commonly referred to as the 100/40 for its type and year of introduction, used a tubular attachment point under the barrel shroud for the bayonet, an adjustable rear leaf sight, and can sometimes be seen with a wire bipod. These early models were all manufactured at the Army’s Kokura arsenal, with approximately 10,000 examples being completed. The airborne version could be disassembled with the stock folded and packed into a carry bag that is attached to the paratrooper’s chest. It would then be assembled on the ground and put into action.
The second model of Type 100 (100/44) introduced in 1944, is a simplified version intended to lower production time and reduce costs. The tubular bayonet fixture was eliminated in favor of a more traditional bayonet lug, the rear sight was changed to simple sheet metal, and the front end of the wood stock was shortened. The Japanese also added a compensator to the muzzle to aid in controllability during full auto fire. Later versions of the second model would also have a wooden buttplate. Roughly 15,500 of these later production guns would be produced by the Nagoya arsenal.
The Type 100 was a simple open bolt, blowback action similar to the European designs that the Japanese were familiar with. One major improvement, however, was the use of replaceable firing pins. Most submachineguns of the era had the firing pin as a component machined directly into the bolt face. If this pin were damaged or broken, the entire bolt would have to be repaired requiring additional machine work at a repair facility or returned to the factory. Instead of having the firing pin incorporated into the bolt as a single machined part, they used threaded firing pin inserts that would thread directly into the bolt face. If the weapons firing pin were damaged, it could be easily replaced in the field, without requiring it to be sent to a repair facility. Quite forward thinking for the time. The Type 100 was fed from a 30-round box magazine inserted into the left side of the receiver. These magazines had to be drastically curved to accommodate the bottlenecked case of the 8x22mm Nambu cartridge. This curve led to several issues with the weapon, notably feeding reliability and complaints that the magazine would get snagged easily in heavy jungle foliage. The Type 100 had a rate of fire of approximately 450 rounds per minute. Firing the Type 100 with the 8mm Nambu ammunition and slow rate of fire made the Type 100 quite controlible in full auto.
The disassembly of the Type 100 is accomplished by rotating the disassembly lever on the right rear of the receiver counterclockwise 180 degrees and removing it from the right side. This allows you to remove the recoil spring guide and recoil spring. Pull the bolt to the rear with the charging handle and remove the charging handle through a notch in the receiver. The bolt can then be pushed backward out of the receiver.
Ultimately, the Type 100 was too little too late for the Japanese with only a little over 25,000 units produced, many of which never left mainland Japan. They were never fielded in enough quantities to have much of an effect in combat. As the war progressed, the Japanese were in desperate need for raw materials and shipping lanes were constantly harassed by allied air and naval power. Production was diverted away from smaller projects and manufacturing focused on producing as many rifles and machineguns the Japanese could muster. The Type 100 still lives on in video games and pop culture as an iconic piece of Japanese World War Two weaponry and can still be found in limited quantities in the US collectors’ market as registered machineguns, and deactivated display pieces.
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