We’ll first discuss how to unlock and level up the TEC-9, including an overview of the weapon. We will then discuss tactics, the best attachments and then the best perks for the TEC-9.
First, starting with an overview. The TEC-9 is unlocked through the season 5 Battle Pass at level 31. It starts out being a semi-automatic submachine gun and ends up being one of the most powerful full auto submachine guns in the game, if you can endure levelling it up to level 46 to unlock the Full Auto Repeater muzzle attachment. It has high damage, low recoil and is easy to handle. At around weapon level 20 you will unlock the Burst Fire Repeater muzzle which helps make the TEC-9 easier to use.
Let’s now discuss tactics. As you level the TEC-9, initially it will only be semi-automatic. This puts you at a significant disadvantage to full auto weapons, so you will need to play more slowly and be ready for enemies. Once you unlock burst fire, the TEC-9 is easier to use and you can become more aggressive. I will focus most of the guide on the full auto version, as that is the most powerful configuration. In full auto mode, the TEC-9 is quite strong which means you can be extremely aggressive. You eliminate enemies much faster than with most submachine guns, giving you a significant edge over enemies. With attachments and perks you can boost your mobility significantly and become a target that is difficult to hit by strafing as you fire at enemies. The high mobility will help you reach the areas of maps that submachine guns shine in, which are close quarter engagements where you can surprise enemies, as well as confuse your enemies by frequently changing position. However, you will be at a big disadvantage at medium and long range to assault rifles and snipers, so be sure to avoid wide, open areas, especially those that have good cover overlooking them.
Moving onto attachments, we will focus on boosting the speed of the TEC-9 through increased mobility and handling. First, pick your favourite sight, my preference is the Microflex LED. Also, be sure to pick the Full Auto Repeater Muzzle attachment once you unlock it. Now onto the attachments that boost your speed, the Bruiser Grip underbarrel attachment increases your overall mobility as well as the sprint, shooting and aim move and walking speed. This will help you get close to enemies more quickly. The SASR Jungle Grip handle protects you from flinching and reduces the aim down sight time so you will be ready for enemies faster. The Vandal Speed Loader increases the Reload Quickness as well as the max starting ammo, helping you get ready for enemies more quickly after a fight. Be sure to reload after every engagement due to the low ammo of the TEC-9.
Moving onto perks, there are many perks that will be helpful so use the Perk Greed wildcard so that you can pick two perks for each slot. Tactical Mask and Flak Jacket protect you from enemy tactical and lethal equipment so you can be aggressive without being slowed down by flashbangs, stun grenades and other lethal equipment. The TEC-9 doesn’t come with a lot of ammo, so use Scavenger to refill ammo from fallen enemies. Take Quartermaster together with the Stimshot equipment to be able to heal up between contested engagements more quickly and continue your aggression without interruption. For the third slot, take Gung-Ho to move quicker whilst reloading and using equipment to help you evade enemy fire if you run dry in the middle of a fight. Take Ninja to hide your footsteps so that you don’t give away your position to nearby enemies.
In summary, the TEC-9 is one of the best guns in the game after you equip it with the Full Auto Repeater muzzle. Here are all the attachments

And here is the complete class setup for the TEC-9 submachine gun in Call of Duty: Black Ops – Cold War.
