The very idea of unification of the small arms based on a singular was probed in the USSR earlier than it was done in other coun¬tries and implemented at a more full extent. In 1961 the RPK (Kalashnikov light machine gun, Index 6P2) developed on the bases of the AKM assault rifle was adopted for service.
The RPK light machine gun in terms of its design bears strong resemblance to the assault rifle and the major lot of its parts and units are interchangeable. The major differ¬ences between them constitute a more long and heavy barrel, folded bipods, and a large capacity magazine. The barrel of 590 mm long permitted to increase an effective range of fire up to 800 meters and the thick¬ness of its walls allowed it to deliver more intensive fire. The use of a bipod enhanced accuracy of fire from a support position. The shape of the stock derived from the RPD machine gun permitted to hold it with
the left hand during the fire. 
The sight has a device to introduce side deflection correc¬tions. The magazine system of cartridge feeding forced developers to develop a 40-round box magazine and 75-round disk magazine. The RPK magazines are inter¬changeable with that of the assault rifle.
The RPKS (6P8) version with the similar folded to the left stock was developed for the air borne troops. The RPKN and RPKSN versions can be equipped with night sights. The extensive unification of parts and units with AKM simplified at large extent the RPK production and its master¬ing in the field environment. The Vyatsko-Polyansky Machine-Building Plant «Molot» launched the machine gun in production.
The RPK machine gun is operational in more than 20 countries of the world and in a number of countries are made its dupli¬cates or variants.