A sub machine gun describes a series of firearms that are smaller than assault rifles and fire pistol-caliber ammunition. SMGs are used all over the world in military and law enforcement applications, and are also used for criminal acts by certain criminal groups. There are a big number of sub machine guns in the Grand Theft Auto series including the Micro Uzi, Micro SMG, Thompson Machine Gun, Uzi Submachine Gun, MP5 (MP10 in Grand Theft Auto IV), MAC-10, Tec-9 and the Scorpion. SMGs are a staple of the Grand Theft Auto games in that they provide more firepower than a pistol, and are more easily wielded than assault rifles. SMGs are found in great supply throughout all games, whether through gun shops, gang members, high-level law enforcement, or just laying around the city.
The SMG rendition in Chinatown Wars is undoubtedly a HK MP5A3, however the barrel appears to be "snub-nosed" (Stubby and short). The stock is concealed so that it is more portable and can be sprinted with and used in drive-bys. It has a fast rate of fire and good accuracy. It is available when the Fully Cocked Upgrade is purchased.