AK-74
The AK-74 (Kalashnikov Automatic Rifle, Model 1974 (Russian: Автомат Калашникова образца 1974 года) is a 5.45mm assault rifle developed in the early 1970s in the Soviet Union by Mikhail Kalashnikov. It was developed from the earlier AKM (itself a refinement of the AK-47) and introduced in 1974. The rifle first saw service with Soviet forces engaged in the Afghanistan conflict.[1] Presently, the rifle is used by the majority of countries of the former USSR. Additionally, unlicensed copies were produced in Bulgaria (AK-74 and AKS-74U), China (Type 88), the former East Germany (MPi-AK-74N, MPi-AKS-74N, MPi-AKS-74NK) and Romania (PA md. 86).
Design details
The AK-74 is an adaptation of the 7.62mm AKM assault rifle and features several important design improvements.[1] These modifications were primarily the result of converting the rifle to the intermediate-caliber 5.45x39mm cartridge, in fact, some early models are reported to have been converted AKMs, with the barrel resleeved to 5.45x39mm.[3] The result is a more accurate and reliable rifle than the AKM.[1] The AK-74 and AKM share an approximate 50% parts commonality (interchangeable are most often pins, springs and screws).
The rifle’s operation during firing and reloading is identical to that of the AKM.[4] After ignition of the cartridge primer and propellant, rapidly expanding exhaust gases are diverted into the gas cylinder above the barrel through a vent near the muzzle. The build-up of gases inside the gas cylinder drives the long-stroke piston and bolt carrier rearward and a cam guide machined into the underside of the bolt carrier rotates the bolt approximately 35° and unlocks it from the barrel extension via a camming pin on the bolt. The moving assembly has about 5.5 mm (0.2 in) of free travel which creates a delay between the initial recoil impulse of the piston and the bolt unlocking sequence, allowing gas pressures to drop to a safe level before the seal between the chamber and the bolt is broken. Like previous Kalashnikov-pattern rifles, the AK-74 does not have a gas valve; excess gases are ventilated through a series of radial ports in the gas cylinder. Since the Kalashnikov operating system offers no primary extraction upon bolt rotation, the AK-74 bolt has a larger extractor claw than the 7.62mm AKM for increased extraction reliability.[5] Other minor modifications were made to the bolt and carrier assembly.
The rifle received a new barrel with a chrome-lined bore and 4 right-hand grooves at a 200 mm (1:8 in) rifling twist rate. The front sight base and gas block were redesigned. The gas block contains a gas channel that is installed at a 90° angle in relation to the bore axis. A pair of support brackets are cast into the gas block assembly and are used to attach a BG-15 or GP-25 under-slung 40 mm grenade launcher. The forward section of the front sight base features a threaded collar that is used to screw in a newly-designed multifunction muzzle device (performing the role of a muzzle brake, recoil compensator and flash suppressor) or a blank-firing adaptor. The muzzle device is held in place by a spring-loaded button and is quickly detachable. The distinctive muzzle brake features a large expansion chamber, two symmetrical vertical cuts at the forward end of the brake and three vent holes positioned to prevent muzzle climb and lateral shift to the right (for right-handed shooters). A flat plate near the end of the brake produces a forward thrust when emerging exhaust gases strike its surface, eliminating nearly all felt recoil. The muzzle brake prevents backblast from reaching the firer, although it is reported to be harsh on bystanders as the muzzle gases are dispersed to the sides.
Variants
AKS-74
The AKS-74 ("S"—So skladnym prikladom) is a variant of the AK-74 equipped with a side-folding metal shoulder stock, designed primarily for use with air assault infantry and developed alongside the basic AK-74. Unlike the AKMS's somewhat fragile underfolding stock (modeled after the MP 40 submachine gun stock), the AKS-74 stock is fabricated from stamped sheet metal struts, machine pressed into a "U" shape and assembled by punch fit and welding. The stock has a triangular shape; it lacks the folding shoulder pad found on the AKMS stock and is folded to the left side of the receiver. The hinged stock is securely locked in its extended position by a spring-loaded button catch located at the rear of the receiver, on the left side. When folded, the stock is held closed by a spring-loaded capture hook situated on the left side at the front of the receiver housing. A rear-mounted sling swivel is also provided on the right side at the beginning of the stock frame.
AKS-74U
In 1979, a shortened carbine variant of the AKS-74 was adopted into service with the Red Army: the AKS-74U (U—Ukorochenniy), which in terms of tactical deployment, bridges the gap between a submachine gun and an assault rifle. It is intended for use mainly with special forces, airborne infantry, rear-echelon support units and armored vehicle crews. 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). 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 enhances the recoil impulse by supplying the gas system with residual gases from the barrel. 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 (2,952.8 ft/s) to 735 m/s (2,411.4 ft/s) resulted in a decrease in effective range (the effective hitting distance for a "running"-type silhouette target was reduced from 625 to 350 m). 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 blank cartridges and the rifle is cycled manually in this mode of operation. 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).
AK-74M
In 1991 the Izhmash factory in the city of Izhevsk began production of an improved variant of the AK-74 – the AK-74M (M – Russian: Модернизированный; Modernizirovanniy or "modernized") assault rifle. Apart from several minor production improvements the rifle also features a new synthetic stock made from a black, glass-filled polyamide that is shaped like the AK-74 fixed stock, but also folds like in the AKS-74. Additionally the AK-74M uses a reinforced muzzle device and dust cover. Each AK-74M is fitted with a side-rail bracket for mounting optics. The AK-74M would have been adopted by the Soviet Union as the standard service rifle, and has been accepted as the new service rifle of the Russian Federation.
AK-100 series
The AK-74 was also the basis for the new Russian family of Kalashnikov firearms: the 5.56 mm AK-101 standard rifle and 5.56 mm AK-102 carbine (both use the NATO-standard 5.56x45mm cartridge), 7.62 mm AK-103 assault rifle and 7.62 mm AK-104 (both chambered for the 7.62x39mm M43 round) and the 5.45 mm AK-105 carbine (adapted to use 5.45x39mm M74 ammunition). The AK-101, 102, 103 and 104 are destined primarily for export, while the AK-105 is slated to replace the AKS-74U with the Russian Armed Forces.
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