PP-19 Vityaz

The PP-19 Vityaz (also known as the PP-19-01 “Vityaz-SN”) is a 9×19mm Parabellum submachine gun developed in 2004 by Izhmash (now Kalashnikov). It is based on the AK-74 and offers a high degree of parts commonality with the AK-74. The gun is directly developed from the PP-19 Bizon. It is the standard submachine gun for all branches of the Russian military and police forces. "Vityaz" (витязь) is Russian for "knight".
Design details.
The PP-19 Vityaz is a selective fire submachine gun that uses a simple closed bolt, straight blowback method of operation. As such, it has no gas system and the internal components have been modified accordingly. The bolt carrier with integral charging handle is similar to AK-family, however the piston rod and rotary bolt were removed and a weight on the bolt extends into the previous gas tube. The return spring and guide rod are almost identical to those of the AK-family.
The PP-19 Vityaz has a four-groove barrel with a 240 mm (1:9 in) right-hand rifling pitch. It is chambered for the 9×19mm Parabellum pistol cartridge and will also fire the new high-pressure armour-piercing 7N31 round that can penetrate soft body armour. The gun is fed from a 30-round box magazine and comes with a fastening device that joins two magazines together. Its muzzle brake has three small rectangular ports on each side that serve to reduce muzzle rise, however their main purpose is to protect the muzzle from damage. It can be equipped with a detachable sound suppressor.
The PP-19 Vityaz shares the same trigger and safety mechanisms as the AK-74 rifle. The selector lever is placed on the right side of the receiver, above the trigger, and has three settings: the uppermost "safe" setting disables the trigger and physically blocks the charging handle; the middle position (marked "АВ") enables fully automatic fire and the lowest position ("ОД") activates the semi-automatic function of the trigger. It utilises the AKS-74 shoulder stock, which folds to the left side of the receiver. The pistol grip is identical to the grip of the AK-100 series and is made of a black fiberglass-reinforced polyamide. The forearm has attachment points for laser target designator, tactical flashlight and fore grip.
The PP-19 Vityaz is provided with two types of rail system for mounting various optical or collimator sights. A Picatinny rail on top of the receiver or a dove-tail side rail, and it also has the standard AK-type front and rear sights.
Variants.
Vityaz.
The original version of the rifle with a standard side rail and no railed dust cover. 
Vityaz-SN.
The Vityaz-SN removed the side rail and added the railed dust cover. 
PPK-20.
PPK-20 is a further modernisation of the PP-19 Vityaz, developed and manufactured by Kalashnikov Concern. The PPK-20 uses the AK-19 stock as well as being issued with AK-9 style handguards and a new suppressor. 
Saiga-9.
The Saiga-9 is a semi-automatic pistol-caliber carbine version of the PP-19 Vityaz with 345 mm barrel sold on the Russian civilian market by Kalashnikov.
KR-9.
In the United States, Kalashnikov USA (not associated with the Kalashnikov Concern) manufactures an 9.25" barrel clone called the KP-9, and a 16" barrel clone called the KR-9.