Submachine Gun <br>
A submachine gun is a pistol-caliber, magazine-fed, individual automatic firearm. In military environments they are traditionally deployed in special operations commando units where mobility is key, or tank crews where space inside the vehicle is tight. In police environments they are deployed in counter-terrorist or special weapons units. 
Since they usually have longer barrels than pistols submachine guns make more efficient use of pistol ammunition and are effective out to about 100 meters, though traditionally they are deployed at shorter distances. They are usually shoulder-fired for better accuracy.