AKS - 74U

By Soviet TTT (тактико-технические требования) order number 008407 from 19.17.1973 a design competition (codenamed "Modern" - Модерн) was started for the adoption of a fully automatic carbine, no doubt inspired by observing the US experience in Vietnam with theXM177. The Soviet planners also drew from the unsolicited design AO-46 built in 1969 by Peter Andreevich Tkachev, which weighed only 1.9 kg. The TTT specifications required a weight no greater than 2.2 kg, a length of 75/45 cm with the stock unfolded/folded, and a muzzle velocity of at least 700 m/s. The competition was joined by designs of M.T. Kalashnikov (PP1), I.Y. Stechkin (TKB-0116), S.G. Simonov (AG-043), A.S. Konstantinov (AEK-958), and E.F. Dragunov (who called his model "MA"). Kalashnikov also presented an additional design (A1-75) which differed from PP1 by having a modified muzzle for flash and noise suppression. By 1977 the GRAUdecided to adopt Kalashnikov's model, which was largely a shortened AKS-74, because it was no worse than the competition in terms of performance and promised significant production cost savings by utilizing existing equipment for the AK-74 line. A final round of large scale testing with Kalashinkov's model was performed by airborne divisions in the Transcaucasian Military District in March 1977. The AKS-74U ("U" — Russian: укороченный; Ukorochenniy, or "shortened") was officially adopted in 1979, and given the official, but seldom used GRAU designation 6P26.

In terms of tactical deployment, the AKS-74U bridges the gap between a submachine gun and an assault rifle. It was intended for use mainly with special forces, airborne infantry, rear-echelon support units and armored vehicle crews. It is still used in these roles, but has been augmented by various submachine guns, and the AK-105. It is also commonly used by law enforcement; for example, each urban police foot patrol is issued at least one.

The rifle's compact dimensions, compared to the AKS-74, were achieved by using a short 210 mm (8.3 in) barrel (this forced designers to simultaneously reduce the gas piston operating rod to an appropriate length). In order to effectively stabilize projectiles, the barrel’s twist rate was increased from 200 mm (1:8 in) to 160 mm (1:6.3 in) to adapt the AKS-74U for muzzle velocities of 720 m/s (2,362 ft/s) and higher. A new gas block was installed at the muzzle end of the barrel with a new conical flash hider combined with a cylindrical muzzle booster, which features an internal expansion chamber that increases the weapon's reliability. The booster supplies an increased amount of residual gas from the barrel for the gas system. The chrome-lined muzzle booster also burns any remaining propellant thus reducing the gun's signature. The muzzle device locks into the gas block with a spring-loaded detent and features two notches cut into the flash hider cone, used for disassembly using the supplied cleaning rod. The forward sling loop was relocated to the left side of the carbine and the front sight was integrated into the gas block.

The AKS-74U also has a different sighting system with a U-shaped flip sight instead of the standard sliding notch rear sight. This sight has two settings: "P" (calibrated for firing at 350 m) and "4–5" (used for firing at distances between 400–500 m). The rear sight is housed in a semi-shrouded protective enclosure that is riveted to the receiver's top cover. This top cover is integral with the gas tube cover and hinged from the barrel trunnion, pivoting forward when opened. Both the gas tube and handguard are also of a new type and are shorter than the analogous parts in the AKS-74.

The AKS-74U is significantly more maneuverable in tight quarters than the AKS-74; however, the significant decline in muzzle velocity from 900 m/s (2,953 ft/s) to 735 m/s (2,411 ft/s) resulted in a decrease in effective range (the effective hitting distance for a "running"-type silhouette target was reduced from 625 m (684 yd) to 350 m (383 yd). The carbine cannot mount a bayonet or standard under-barrel grenade launcher. However, a suppressed 30 mm BS-1 grenade launcher was developed specifically for that platform that fires a high-explosive dual purpose (HEDP) grenade. The grenades for the BS-1 are launched by special blank cartridges that are inserted into the grenade launcher via a detachable magazine. The majority of AKS-74U carbines were manufactured at the Tula Arms Factory rather than Izhmash. The AKS-74U was also used as the basis for several other unique weapons, including the bullpup OTs-14 Groza specialist carbine, and the Gepard series of multi-caliber submachine guns (none of which evolved past prototype stage).

In the United States, the AKS-74U is called a "Krinkov". The origin of this term is uncertain. A hypothesis was circulating that the name came from the mujahadeen who supposedly had captured a high-ranking Soviet officer armed with an AKS-74U, and that they had named it after him. However, investigation by Patrick Sweeney could not confirm this hypothesis, for no Soviet officer with a resembling name was captured in Afghanistan. US journalist C. J. Chivers reported that the gun was nicknamed "the Osama" in Jihadist circles, after Osama bin Laden was photographed next to an AKS-74U.