Type 79 submachine gun is rather unusual for its class as it is very lightweight and uses locked breech, gas operated action instead of more traditional (for SMG) blowback action. This weapon was (and probably still is) widely used by PAP (Chinese police).
Type 79 submachine gun uses gas operated, rotary bolt action with short stroke gas piston, located above the barrel. Bolt group is more or less an adaptation of the Type 56 (AK) assault rifle, with similar bolt carrier (less gas piston) and a rotary bolt with two locking lugs. Receiver is made from steel stampings. Fire mode selector / safety switch is also patterned after Type 56 (AK) assault rifle, and allows for single shots and full automatic fire. Type 79 fires from closed bolt and uses conventional hammer-fired mechanism. Box magazines hold only 20 rounds of ammunition. Shoulder stock is made from stamped steel and folds up and forward when not in use.