Tokyo Arsenal experimental submachine guns

Koishikawa 1927

From 1923 - 1930, Tokyo Arsenal (then merged with Koishikawa Arsenal) developed two experimental submachine guns for Japanese trials. These guns were credited to Toshio Takazeki and were chambered in the domestically-produced 8x22mm Nambu cartridge. The first prototype, often referred to as the "Model 1927", was submitted in 1927 and had a distinctive Thompson-like appearance, with a forward grip and a round drum magazine. However, the feed was actually derived from the Hotchkiss type (a machine gun that had considerable influence on the development of Japanese automatic weapons), with the drum simply acting as a rotating spool for a series of tape-metal strips, which fed into the right side of the receiver and ejected from the left. Feed from the drum magazine totaled 50 rounds. A 30-round box magazine was also offered with the gun. The action was blowback-operated with a pneumatic buffer.

Koishikawa 1928
Cross-section sketch of the Model 1928 submachine gun by Tokyo Arsenal.

The following year, the "Model 1928" prototype was submitted. This was a different design, utilizing a closed-bolt action and a trigger device that gave only single shots or two-round bursts. The magazine capacity was only 18 rounds.

Both prototypes were trialed against each other, and against several foreign designs including the Lahti submachine gun from Finland, the Thompson from the United States, and the SIG-Bergmann from Switzerland. The fire rate of the Model 1927 prototype was reportedly very high at 1,200rpm and the strip-feed predictably gave frequent stoppages. The bolt buffer also gave trouble and would not stand up to sustained fire. The Model 1928 prototype had issues of its own, suffering a broken firing pin during tests which eliminated it as a viable possibility. Both guns were demonstrably inferior to the foreign submissions and the SIG-Bergmann was favoured, resulting in the Imperial Japanese Navy placing an order for several hundred SIG-Bergmanns in 1930 which they issued to the Special Naval Landing Forces. Work on the Tokyo Arsenal SMGs ceased.

The fate of the Model 1928?


While there are some surviving photos of the Model 1927 prototype, only patent sketches of the Model 1928 seem to have surfaced. Recently however I came across a photograph which I think may show the Model 1928 - although it is difficult to prove. A photo taken in late 1945 for LIFE magazine depicts US Marines at the Yokosuka Naval Arsenal with piles of captured Japanese rifles, including some unidentified self-loading prototypes. Closest to the camera is a small pile of submachine guns, probably mostly Type 100s - however there is one gun in amongst that pile that is clearly not a Bergmann or a Type 100, but a mystery prototype. What is this weapon? It occurred to me almost instantly that it shares some similarities in shape to the patent sketch of the Model 1928, and for lack of any other Japanese weapons that match its design, I assume that it is indeed this gun.

Unfortunately, we will never know for sure, as the caption accompanying this photo explains that these weapons were about to be destroyed! Thus several Japanese prototypes were probably lost during the American occupation after World War II.

Back to database