The Intratec TEC-9, TEC-DC9, KG-99 and AB-10 are a line of blowback-operated semi-automatic pistols. They were developed by Intratec, an American subsidiary of the Swedish firearms manufacturer Interdynamic AB. Introduced in 1984, the TEC-9 was made of inexpensive molded polymers and a mixture of stamped and milled steel parts. The simple design of the gun made it easy to repair and modify. The TEC-9 developed a negative reputation for its association with organized crime, street gangs and mass shootings in the 1990s, with it most notably being used during the 101 California Street shooting and the Columbine High School massacre. However, it was a commercial success, with over 250,000 being sold. History Interdynamic AB, a Swedish firearms manufacturer based in Stockholm, designed the Interdynamic MP-9, intended as an inexpensive 9mm submachine gun based on the Carl Gustav M/45 for military applications. The firearm was initially intended for adoption by the South African apartheid government, though it was rejected and shipped to various other nations. Ultimately, Interdynamic did not find a government buyer. As a result, the weapon was taken by lead designer George Kellgren to the United States domestic market as an open-bolt semi-automatic pistol, redesigned to eliminate its collapsible stock and vertical foregrip features per the National Firearms Act of 1934 and marketed under the subsidiary Interdynamic USA brand. Still, the design was deemed too easy to convert to an automatic weapon. Due to this, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) forced Interdynamic USA to redesign the firearm into a closed-bolt system, which was harder to convert to an automatic weapon. This variant was called the KG-99, and was popularized when it made frequent appearances on the popular television show Miami Vice, where it was legally converted to full auto by Title II manufacturers. The KG-9 and KG-99 have an open-end upper receiver tube where the bolt, recoil springs, and buffer plate are held in place by the plastic/polymer lower receiver frame. This design only allows for 9mm ammunition, and if a heavier grain ammunition or hot loads are used, the plastic lower receiver will fail or crack, rendering the firearm unusable. Later versions of the TEC-9 and AB-10 had a threaded upper receiver tube at the rear and a screw-on end cap to contain the bolt, recoil spring, and buffer plate even if removed from the lower receiver, solving the problem of lower receiver failure