The SCK-65 submachine gun was developed during early 1960s by Japanese company Shin Chuo Kogyo (SCK), and subsequently adopted by Japanese Self-Defense Forces. Due to strict Japanese laws, this submachine gun was never exported out of Japan, and thus is rarely known. The SCK-66 submachine gun, which appeared a bit later, was externally similar to Model 65 but had lower rate of fire.
The SCK-65 submachine gun is a simple blowback weapon which fires from open bolt, in full automatic mode only. The gun is somewhat unusual as it has ejection port on the left side of the gun. The ejection port is fitted with dust cover, which must be manually opened before the gun can be loaded or fired, as it has a small projection on its underside which locks the bolt when cover is closed. This manual safety feature is complemented with automated grip safety in the form of a lever, located at the rear of the extended magazine housing. The disengage this automated safety, operator must grip the lever with his left hand and push it firmly forward, against the magazine housing. The cocking handle is located on the right side of the gun and does not move when gun is fired. The barrel is enclosed into the tubular jacket, which, surprisingly, has no cooling ports or slots. The side-folding shoulder stock is made from thin steel tubes.