A new standardised family, chambered for the 5.45 mm assault rifle cartridge and comprising four 5.45 mm assault rifle models and four 5.45 mm light machine gun models with two types of butt-stocks, entered the inventory under the decree of the Central Committee of the Communist Party and the USSR Council of Ministers dated 18 January, 1974 and the follow-up order of the USSR Defence Minister dated 18 March, 1974. The 5.45 x 39 mm low-recoil cartridge was expected to be fired from assault rifles and light machine guns from the very outset. Moreover so that the new cartridge allowed a gunner to carry a great ammunition load.
The new family of small arms comprised 6P18 RPK-74 fixed-butt light machine guns and 6P19 RPKS-74 folding-butt light machine guns. They differ from the AK-74 assault rifle in the same way as the RPK light machine gun differs from the AKM assault rifle - a longer barrel, a folding bipod, and a large-capacity magazine. New elements include a muzzle attachment and a magazine. The muzzle is fitted with a slotted flash suppressor, which can be replaced with a blank firing attachment.
Just like the AK-74 assault rifle, the RPK-74 has a notch on the left side of the bolt carrier assembly to reduce the weight, while a rectangular nib on the bolt carrier bottom prevents the recoiling bolt from engaging upper cartridges in the magazine. The bolt is smaller and does not have a ring-shaped bolthead recess, the firing pin protrudes over the breeching face. The bolt assembly is fitted with an open extractor. The gas cylinder with a handguard on its rear end has a spring washer, which braces the gas cylinder and the gas chamber.
The RPK-74 is equipped with a U-notch sliding-leaf rear sight with a windage knob. The light machine gun primarily fires short bursts of five to seven rounds. A reduced recoil and a shorter time it takes the bullet to reach the target improved the accuracy of fire by approximately 1.5-fold as compared with that of the 7.62 mm RPK light machine gun.
Low-recoil small arms cartridges include the 7N6 cartridge with the PS steel-cored bail bullet; the 7T3 tracer round; the 7T3M cartridge with an upgraded tracer bullet; an armour-piercing cartridge with the BP bullet; the 7N10 cartridge with the PP enhanced-penetration bullet; the 7Kh3 blank round; and a training round. A cartridge with the PS bullet, weighing 3.45 g, weighs 10.2 g, i.e. the weight of the ammunition load, totaling the same number of cartridges, is 1.5-fold lighter than that of the ammunition allowance, made up of 1943-vintage rounds.
Ammunition feed is from a 45-round double-column chequerwise curved box plastic magazine. There is a special device for loading a magazine from a clip. The RPK-74 and the RPKS-74 are only fed from box magazines, as the drum magazine option was eliminated for economic reasons.
The original wooden stock and Fore-end were gradually replaced with plastic (glass-nylon composite) ones.
It is worth mentioning that the USSR was the first to standardise squad-platoon-level small arms of both standard and small calibre. This process was facilitated by the high reliability and the modernisation potential, inherent in the Kalashnikov design.
The RPK-74 and its versions are in service with Russia, former Soviet republics, and a number of foreign countries.
East Germany, Poland, Yugoslavia, Libya, and Finland used to manufacture replica of the Soviet RPK and RPK-74 light machine guns and their versions, or develop their own models of Kalashnikov light machine guns.
There are also «night» versions of the 5.45 mm light machine gun. The rail on the left side of the receiver mounts passive night sights with the help of the standard dovetail attachment.
Depending on the model of a night sight, there are the following versions: RPK-74N1, fitted with the NSPU (1PN34) sight; RPK-74N2, fitted with the NSPUM (1PN58) sight; and RPK-74N3, fitted with the NSPU-3 (1PN51 sight). The light machine gun can also be equipped with the NSPU-5 (1PN83) night sight. The latter has a magnification of 3.5 fold and is capable of detecting a man at a range of up to 300 m. Another option is the 1P29 versatile sight with a four-fold magnification and a weight of 0.8 kg. Low-intensity conflicts also saw the use of RPK-74N light machine guns fitted with optical instead of night sights. The loaded weight of the RPK-74N1 with the NSPU sight amounts to 7.66 kg.