The PP-19-01 Vityaz is a development of the PP-19 Bizon, a submachine gun developed by Izhmash at the request of the Russian Interior Ministry in the early 1990s. The Bizon design team included the sons of both Mikhail Kalashnikov and Evgeniy Dragunov, and they created a well-designed unlocked blowback adaptation of the AK system using a 64-round helical drum magazine and chambered for the 9x18mm Makarov cartridge. In actual use, the magazine proved unreliable (shocking…) and in the early 2000s a new version was developed based on the experience with many iterations of the Bizon.
This new version was the Vityaz, chambered for 9x19mm Parabellum and using a conventional 30-round double stack, double feed polymer magazine. It was made as a select fire submachine gun, but also offer in semiauto form on the civilian market as the Saiga-9. Kalashnikov USA is manufacturing a virtually indistinguishable copy here as the KP-9 pistol (or KP-9 rifle, with a 16 inch barrel). The example in this video is a KP-9 that has been registered as a short-barreled rifle and fitted with the appropriate side-folding stock to duplicate the form of a Vityaz.
Thanks to Kalashnikov USA for providing the KP-9 for this video!