The AKS-74U's compact dimensions were achieved by using a short barrel (this forced designers to simultaneously reduce the gas piston operating rod to an appropriate length). The AKS-74U is approximately lighter than the NATO equivalent
XM177, and shorter with the stock folded.
Operation Due to the shortening of the operating mechanism, the
cyclic rate rose slightly to around 700 rounds per minute. In order to effectively stabilize projectiles, the barrel's twist rate was increased from 200 mm (1:7.87 in) or 37 calibers
rifling twist rate to 160 mm (1:6.3 in) or 29.6 calibers rifling twist rate to adapt the AKS-74U for muzzle velocities of and higher. A new gas block was installed at the muzzle end of the barrel with a
muzzle booster, which features an internal expansion chamber inside the cylindrical section of the booster while the conical end acts as a nozzle to increase net pressure inside the gas chamber by supplying an increased amount of propellant gases from the barrel. The chrome-lined muzzle booster also burns any remaining propellant, which would normally reduce muzzle blast. However, due to the extremely short barrel and conical end of the booster, the muzzle blast is nevertheless extremely large and visible. The muzzle device locks into the gas block with a spring-loaded detent pin and features two parallel notches cut into the edge of the flash hider cone, used for unscrewing it using the cleaning rod. Unlike most Kalashnikov variants there is no provision to store the cleaning rod under the barrel. The front sight was integrated into the gas block/forward sling loop.
Ergonomics The sight height above the bore axis is also approximately higher than the AK-74, due to the combined front sight/gas block, rear sight configuration. The AKS-74U has a different rear sight composed of a U-shaped flip sight on the top cover instead of the standard sliding notch tangent rear sight. This rear sight has two settings: "
П () corresponding to a "point-blank range" battle zero setting and "4-5" (used for firing at distances between ). The rear sight is housed in a semi-shrouded protective enclosure that is riveted to the receiver's spring-loaded top cover. This top cover hinges from a barrel trunnion (hinging where the rear sight on a normal AK74 is located), pivoting forward when opened, which also works to unlock the gas tube cover. Both the gas tube and handguard are also of a new type and are wider and shorter than the analogous parts in the AKS-74. The AKS-74U was used as the basis for several other unique weapons, including the
bullpup OTs-14 Groza specialist carbine which is now in limited service in the Russian military, and the
Gepard series of multi-caliber submachine guns (none of which evolved past prototype stage).
Ammunition For the AKS-74s combined with the 7N6 or 7N10 service cartridges the 350 m battle zero setting limits the
apparent "bullet rise" within approximately relative to the line of sight. Soldiers are instructed to fire at any target within this range by simply placing the sights on the center of mass (the belt buckle) of the enemy target. Any errors in range estimation are tactically irrelevant, as a well-aimed shot will hit the torso of the enemy soldier. The AKS-74U is significantly more maneuverable in tight
quarters than the AKS-74; however, the significant decline in
muzzle velocity to resulted in a reduction in effective range to (the effective hitting distance for a "running"-type silhouette target was reduced from to ).
Accessories The AKS-74U 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. There were some accessories produced for the AKS-74U including a plastic thigh holster and (shorter than standard) 20-round AK-74 type magazines. The rifle utilizes a proprietary 25 mm wide sling that differs from the standard 35 mm AK sling also in construction. The AKS-74U also exists in a version featuring modernized synthetic furniture made from a black,
glass-filled polyamide. == Variant ==