The OTs-12 “Tiss” (ОЦ-14 “Тисс”) compact assault rifle was developed in 1993 on request from the Russian Ministry of Internal Affairs (MVD) as a dedicated urban CQB weapon for SWAT-type teams.
The OTs-12 “Tiss” assault rifle was designed and produced by the TsKIBSOO (Central Design Bureau for Sporting and Hinting Arms), located in the city of Tula. It was, basically, a conversion of the existing AKS-74U compact assault rifles for the 9x39mm cartridges, originally developed for the AS Val suppressed assault rifle. The 9x39mm SP-6 cartridge launched a heavy 16-gram AP (hardened steel core) bullet at subsonic velocities. As a result, the OTs-12 “Tiss” compact assault rifle was envisioned as a sort of super submachine gun, offering increased penetration and stopping power compared to similarly sized weapons that fired 9mm pistol cartridges. Due to a much heavier and slower bullet if was also better suited for urban operations than a 5.45mm rifle, due to much shorter danger range and less chances of the ricochet.
During 1993 and 1994, the TsKIBSOO converted several hundreds of 5.45mm AKS-74U assault rifles to the 9x39mm OTs-12 assault rifle configuration. Those weapons were subsequently issued to a number of OMON and SOBR quick reaction and counter-terrorist (SWAT-type) police units across the Russia. However, the OTs-12 was not so popular among the users, mostly for the lack of spare magazines, which were unique to the gun, and not compatible with anything else except the latter OTs-14, which was also a scarce weapon. As a result, the OTs-12 was soon superseded by the somewhat similar but more versatile 9x39mm SR-3M and 9A-91 assault rifles, which, unlike the Tiss, also offered quick-detachable suppressors as the very useful tactical option. The OTs-12 assault rifle also served as a basis for development of the modular OTs-14 Groza bullpup assault rifle.
The OTs-12 “Tiss” assault rifle differs from the standard AKS-74U in a number of ways. The most obvious changes were the new barrel with its 9 mm bore, its new muzzle brake/compensator, a modified bolt with enlarged face and a new 20-round magazine made from stamped steel. The least obvious but perhaps most interesting change, however, is its redesigned gas system. Due to the relatively low pressures generated by subsonic 9×39 mm ammunition, the gas port and gas block were moved back, to just in front of the chamber. From there, propellant gases were fed forward to the modified AKS-74U gas block via the steel gas tube running above the barrel, inside the handguard. This permitted the use of an unmodified AKS-74U bolt carrier and gas piston. The final change involved its rear sight, which was replaced with an adjustable aperture (diopter) with a rotating knob located on the left-hand side of the rear sight block. The sight has four range settings, for 50, 100, 150, and 200 meters.
Technical Specifications, OTs-12 assault rifle