SMGs are the next best thing in close range combat to having a shotgun. If the Shotguns are the king, these are the stewards. That is, if you are really bad at jokes and want to impress some internet people. The SMG typically has a wider spread, shoots a lot of bullets very quickly, and does low damage per bullet. In short, the name of the game is get close, and track as hard as you can.
SMGs, up until the last patch of season 4, were only small bullet guns, but the addition of the Drum Gun to the mix, (using medium bullets) it has increased damage, the same fire rate as it’s Silenced cousin, and a larger magazine.
The DRUM GUN
The Drum Gun has a lot of damage, but a wider spread than the typical SMG. It is both good for close to medium range combat, but also excellent for destroying builds. The biggest downside to the Drum Gun and also the Tactical SMG is that they do not have perfect accuracy. So, be careful when using all of your medium bullets in a gun that is not very accurate.
The SUBMACHINE GUN
The New Submachine Gun is the buffed replacement for the Tactical SMG, which was added to the VAULT on 7/17/2018. It does slightly more damage per bullet, has the same fire rate, and a fraction of a second more reload time. In almost every way, this gun is better. Still good at only close to near medium range fights, has no perfect accuracy, and does heavy damage to structures.
The SILENCED SMG
Moderate damage and perfect accuracy, the Silenced SMG has the capability to do work at close range, but can also be used for medium and rarely long range fights. Damage falloff is a big deal at long ranges, but you can still harm opponents while staying inconspicuous.
The TACTICAL SMG
The Tactical SMG has the fastest fore rate of all the SMGs but also the lowest damage per bullet. It is the classic SMG, good for build denial and general damage. However, it is not good at medium to long range due to accuracy and damage falloff.