Nambu model I submachine gun appeared around 1932, when the famous small arms designer Gen. Kijiro Nambu introduced an indigeneus weapon of his own design. General Nambu decided to place a high-capacity curved box magazine inside the pistol grip of the weapon, making it noticeably shorter than contemporary rivals while maintaining similar barrel length. This gun, known as the Nambu Type I (some sources also designate is as Type II, first model or Type IIA), was tested by the Imperial Japanese Army in 1936-37 but was rejected as complicated and unreliable. Apparently, small numbers of these submachine guns were manufactured by Nambu factory and used by Japanese Marine units in China in around 1937. During late 1930s Nambu also tried to offer his submachine gun for export sales, but without any success as the gun was chambered for the marginally powerful 8×22 pistol ammunition used only in Japan.
Nambu submachine gun was of simple blowback design, firing from closed bolt. It was fitted with pneumatic rate-reducing buffer at the rear of the tubular receiver. Breechblock (bolt) was pinned to the tubular barrel jacket, which reciprocated around the barrel in fashion similar to typical self-loading pistol. Return spring was placed around the barrel. Severely curved box magazine was inserted into the hollow pistol grip, which was necessarily canted forward, possibly resulting in awkward handling of the gun. Bottom of each magazine was fitted with small folding spade to be used as a support against the ground, when firing from prone position. Nambu submachine gun was fitted with fixed wooden shoulder stock and adjustable rear sight.
|Full text name||Nambu model I submachine gun|
|Caliber cartridge||8x22 Nambu|
|Overall length, mm||620|
|Barrel length, mm||?|
|Weight empty, kg||2.8|
|Magazine capacity, rounds||50|
|Cyclic rate of fire, rounds/min||300-600|