"The TCN4 is a well-balanced and capable SMG." In-Game Description.
The TCN4 SMG is a rapid fire projectile weapon that deals 80 damage per hit. The weapon does not damage armored targets such as base turrets or sensors, but will damage player turrets and force fields. This SMG is one of the best in the game with an excellent firing rate and decent damage. Initially the clip size is a bit small, but this can be improved with upgrades. Even though the bullets travel very fast, it is not a hitscan weapon, requiring you to lead the shots.
The TCN4 SMG should be used to pepper incoming enemies and weaken potential cappers. It lacks a lot of stopping power compared to the Thumper but still deals a high amount of damage in a short period of time. If you are defending the Generator the Thumper is a better option. If you are repairing Base Turrets and Sensors you should use this weapon.