A Sub Machine Gun (SMG) is a weapon used by a Point Man which commonly features a combination of high Rate of Fire (RoF) but low Accuracy. The Sub Machine Gun excels in close combat but falls weak when distances increase. Low accuracy and fairly high recoil makes a steady stream of bullets very hard to produce, which is why SMG users would be wise to stick to close combat, like any Point Man should. A unique aspect about submachine guns is that they can be attached with suppressors, something that cannot be done with an Assault Rifle or a Sniper Rifle.
Since accuracy is not a large factor in close combat, simply spraying should be more than enough to leave your opponent incapacitated.