The OTs-33 Pernach / ОЦ-33 Пернач (multi-flanged mace) is a Russian selective fire, 9×18mm Makarov machine pistol. It was designed to replace the Stechkin APS in various special OMON units within the Russian police, the Russian Ministry of Internal Affairs (MVD) and other paramilitary units. The OTs-33 was developed in 1995 by Igor Stechkin at the TsKIB SOO design bureau, and it went into limited production at the KBP Instrument Design Bureau. Also known as the АП СБЗ-2 (AP SBZ-2). The design was made to resolve the difficulty of controlling recoil in full-auto mode present in the Stechkin APS and simplifying it for combat deployment. The new OTs-33 has a more square shape, which is simpler to manufacture and has a novel operating principle that increases controllability and reduces recoil.
Easily identified by its boxy slide and ambidextrous (visible on both sides) firing selector switch located on the rear end of the slide as well as a detachable shoulder rig / stock. (as seen here: post #3043608)