The TEC 9 is a cheap open-bolt handgun manufactured in the United States between 1980 to 1994 by Intratec. It is based on the Carl-Gustav M/45 submachine gun, more commonly known as the "Swedish K". Originally it was designed as a low-cost alternative to the M/45, but never found a military market. Not wanting to abandon the idea, Intratec put semi-automatic versions onto the civilian market. It gained infamy after criminals found the open-bolt design to be easily convertible to be fully automatic.
In GTA: San Andreas, the TEC 9 shares weapon skill with the Micro Uzi and both level up through the use of either weapon.
In GTA: San Andreas, the TEC 9 is used by all Los Santos based gangs in missions only while it is only used by members of the Grove Street Families until it is replaced by the SMG when all gang tags sprayed over.
In GTA: San Andreas, firing while in a vehicle increases the weapons fire rate tremendously compared to the normal fire rate while on foot.