Because of its defeat in World War 2 (1939-1945), the nation of Japan was heavily restricted in its war-making capacity by the victors. However, amidst the backdrop of the Cold War (1947-1991) between the United States and the Soviet Union, the country was slowly allowed to develop a local arms industry and from this gave rise to several products of note including the SCK Model 65 prototype submachine gun (SMG). This weapon marked the first, and currently only, submachine gun to emerge from Japan in the post-World War 2 period.
The Model 65 was undoubtedly inspired by other existing foreign types with an external similarity akin to the classic Swedish "Carl Gustav" series. It was chambered for the readily-available 9x19mm Parabellum pistol cartridge and operated through a blowback system (open-bolt function). Feeding was by way of a 30-round straight, detachable box magazine which doubled as the foregrip. Iron sights were fitted for some accuracy in ranged fire but this was a close-quarters weapon through-and-through.
The basic design incorporated a rounded, rectangular receiver with a relatively short barrel assembly protruding some distance ahead. The pistol grip was set at the extreme aft-end of the receiver and slung under in typical fashion. The trigger loop was large and gave ready access to the trigger itself. The magazine well was positioned some distance ahead of the trigger group. A cocking handle was set to the right side of the weapon. The SMG incorporated a dust-cover over the ejection port that doubled as a safety catch (as in the American M3 "Grease Gun") and the grip handle also incorporated a safety mechanism similar to that as found on Danish "Madsen" guns. Another Madsen-inspired featured appears to be the side-folding, double-strutted skeletal folding stock.
Design work was had during 1965 and a batch sample was produced by Shin-Chuo Industries (formerly the Nambu Arms Manufacturing Company, now Minebea) with the hope that the submachine gun would someday equip the fighting men of the Japanese Ground Self-Defense Force (JGSDF). The type was actually slated to succeed the aging line of American M3 SMGs then in service with Japanese warfighters.
The original Model 65, also known as the "New Nambu Model 66", had a weight of 4 kilograms with an overall length of 765mm. With the stock folded, the latter value was reduced to 500mm for a more compact footpring. The barrel assembly measured 155mm long and rate-of-fire reached 550 rounds-per-minute.
The Model 65 was followed in development by the Model 66 of 1966. This form was slightly revised internally with a modified bolt and return spring to lower the weapon's rate-of-fire to 465 rounds-per-minute, in effect making the firearm more controllable especially when on full-automatic fire.
At any rate, the Model 65 was not adopted for service by the JGSDF and spent its life in prototype and trials forms only.