I just really like the design. Simple and functional. It looks like it should fire something more powerful than the 7.62×25mm Tokarev.

SinoDefense:
The Type 79 submachine gun is more or less patterned after the Type 56 (AK-47) assault rifle. It uses gas-operated, rotary bolt action with short stroke gas piston located above barrel. The bolt group and fire mode/safety switch are similar to those of the Type 56 rifle. The barrel, receiver, pistol grip, magazine and shoulder stock are all made from stamped steel. The weapon fires 7.62 X 25mm pistol cartridge in either single or fully automatic mode. Ammunitions are fed from a straight box magazine that holds 20 rounds. Shoulder stock folds up and forward when not in use.
Hat Tip: MP.net
I came across a cool photo of an MP5SD with mini-uzi type stock.
Click to expand image.

Hat Tip: MilitaryPhotos.net
This photo has been floating around the internet for quite a long time. I recently saw in on BoingBoing.

This little engraved MP5K is a machinenpistol produced in 1976, “designed at the request of HK South American sales rep, who saw a market for dignitary protection and increased firepower in a small package.” It comes with its own leather “briefcase” carry-case that allows for fast, machine-gun-kelly-style blasts from within the bag
Bryant @ Defense Tech writes about his experience testing the H&K USC .45 carbine
During demonstration firings of the weapon here at Blackwater USA’s training grounds, Military.com was invited to shoot up some targets using the Kriss and, for comparison, H&K’s USC .45 carbine.
Though another submachine gun might have made for a better assessment, TDI obviously was comfortable with the H&K choice for the purpose of evaluating recoil. The Kriss certainly won out, though the H&K did not give a severe kick either, and TDI chief operating officer Chuck Kushell acknowledged his competitor made a fine weapon.
More here.
