AK-47 / AKM (USSR) Type 56 (China)

AK-47 stands for "Avtomat Kalashnikova, model of 1947". AK-47 was designed by M.T.Kalashnikov in the 2nd half of the 1940s, and was adopted by Soviet Army in 1947 as AK. It was manufactured in huge numbers, for both internal use and export. Many countries, such as Romania, Bulgaria, East Germany, PR China and others also manufactured clones of the AK. Main production facility of the AKs was IzhMash - Izhevsk machine building Plant, Izhevsk, Russia.
Technically, AK is select-fire, gas-powered, magazine fed assault rifle. Gas system of the AK uses long stroke gas piston, attached to bolt carrier. AK features rotating bolt with two massive lugs that locks securely into slots, cut in the inner walls of the receiver. The receiver itself was machined from the solid steel bar, receiver cover was stamped from sheet metal. Barrel is attached into receiver permanently, and bore and the chamber are chrome lined.
AK is hammer-fired, select-fire weapon. The fire selector/safety switch is located at the right side of the receiver, and has three positions: "Safe" (upper position), "Auto" (middle), "Single shots" (lower position). The safety switch is somewhat uncomfortable to operate.
AK features open iron sights, with front sight adjustable for wind-age and rear sight adjustable for elevation and marked in 100s of meters, from 100 to 800 meters. Sight radius is too short, when compared to other assault rifles, such as M16.
The stock and grip are made of wood. Shortened variant of original AK, called AKS, was intended for paratroopers and featured folding down metal butt stock.
Original AK was improved in 1959. Original milled receiver was replaced by stamped one, new receiver cover with stamped grooves for greater strength replaced the old plain one, barrel was equipped with screwed-on muzzle flip compensator, that could be replaced by silencer. Special subsonic ammunition with heavier (12 grams) bullet was developed to be used with the silencer. This modified gun was adopted as AKM, and served as a general issue small arm for the Soviet Army until 1974, when small-bore variant of the AKM, AK-74, was adopted. But until now, many AKMs are still in limited service in Russian Army.

Legendary reliability of the AK comes from simple design and overpowered gas drive. When operating in normal condition, the bolt carrier/bolt group moves at high speed and strikes hard against the rear wall of the receiver and against the front wall of the receiver on the way back to close the breech. This somewhat decreases the full-auto fire accuracy, but gives to the system the power needed to operate with seriously fouled and dirty receiver.
Thus, usually, AK require less cleaning under the battle conditions, and less sensitive to powder quality, than other assault rifles, especially ones such as M16, designed with relatively light bolt carrier/bolt groups and direct gas actions without gas pistons.
In general, AKs are extremely rugged and reliable guns, simple to operate and fieldstrip, without any small parts that may be lost in field conditions. They are of average accuracy and not too comfortable to carry and fire, but they do the job they designed to, and do it excellent.
AK is most copied assault rifle in the world. Leaving aside many ex-East-block countries, officially licensed clone of the AK is still manufactured in Finland, as Sako/Valmet. An improved copy of the Valmet is built in Israel as Galil, and the copy of Galil is built in the South Africa as R-4 and R-5. Many other assault rifles, such as FN FNC, bear the marks of the AK design.

QBZ-95 / 97 (People Republic of China)

Caliber: 5.8x42 mm (5.56x45 mm NATO)
Action: Gas operated, rotating bolt
Overall length: 760 mm
Barrel length: 520 mm
Weight: 3.4 kg unloaded
Magazine capacity: 30 rds

The QBZ-95 assault rifles were shown for the first time when PR China took over the Hong Kong in 1997. The PLA soldiers were armed with this bull pup assault rifle. It is chambered for new proprietary Chinese cartridge, 5.8x42mm, and QBZ-97 (export version) is chambered for standard 5.56mm NATO (.223 Rem). The QBZ acronym stands for 'Qing Buqiang Zu' or light rifle family.

Not much is known about this rifle. It is available in full-size or short (carbine) version, and may be equipped with telescopic or night sights, under barrel grenade launcher and bayonet. The ejection port is located at the right side of the receiver so (probably) this rifle is not ambidextrous. The body (stock) of the rifle is made from polymer, as well as magazines.

AKS-74 (USSR)

Caliber, mm: 5.45
Cartridge: model 1974, 5.45x39
Action: Gas operated, rotating bolt with 2 lugs
Magazine capacity, rds: 30
Weight: 3,200 g (with empty magazine without bayonet); 3,500 g (with loaded magazine)
Full length (w/o bayonet): 933 mm
Length w/folded butt: 700 mm
Sighting range, m: 1000
Muzzle velocity, m/s: 900 

AK-74 series of assault rifles is a "direct child" of world-known AK-47. Following the world trend for small-caliber assault rifles, M.T.Kalashnikov created this weapon system for lightweight and low-impulse cartridge 5.45x39. When compared to M16, AK-74 shows a little poorer accuracy, but better reliability in battle environment and lower requirements for cleaning and maintenance during combat.

AK-107, AK-108 (Russia)

Caliber, mm: 5,45x39 (5,56NATO for AK108)
Action: Gas operated, rotating bolt with 2 lugs, balanced bolt-carrier/bolt group to reduce recoil jumping
Length, mm: overall: 943; w. stock folded 700;
barrel length: 415 mm
Sighting range, m: 1000
Weight, g: 3,400
Magazine capacity, rds: 30
Rate of fire, rds/min: 850 . (900 for AK108)

New modification of AK design - this time with balanced automatic gas driven engine. "Balanced" means that this system has 2 opposite moving gas pistons instead of one. main gas piston drives bolt carrier (via gas rod), secondary piston drives compensating mass (via its own rod) in direction, opposite to bolt carrier. This movement greatly reduced muzzle jump and increased accuracy in full-auto mode.

AN-94 "Abakan" (Russia)

Caliber, mm: 5.45
Cartridge: model 1974, 5.45x39
Action: Gas operated, rotating bolt; moving barrel-receiver-gas drive group for delayed recoil action
Overall length: 943/728mm
Barrel length: 405mm
Magazine capacity, rds 30
Sighting range, m: 700
Cyclic rate of fire, rds/min: 1800/600 (1800 in 2 rds fixed burst mode or 2 first shots in full auto mode, all following shots in full auto - w 600 rds/min)
Weight without magazine: 3850g

This assault rifle was created for the Russian army as a replacement for the A K-74 with greatly improved accuracy. This gun is designed with "delayed blowback impulse" gas driven automatics. This gun has 2 rates of fire: 1800 rds/min in fixed burst length 2 shots mode or in full auto mode - for first two rounds (all following rounds in the same burst will be fired with a rate of 600 rds/min). This mode "delays" blowback for first 2 shots and gives greater accuracy. Being formally accepted by Russian Army, it is very doubtful that this AR will replace the "good old" AK-74 in mass service anytime soon.

AEK-971 (Russia)

Caliber: 7.62x39mm and 5.45x39mm
Action: Gas operated, rotating bolt, balanced
Overall length: 965 mm
Barrel length: ?? mm
Weight: 3.3 kg without magazine
Magazine capacity: 30 rds, all standard AK-47 or AK-74 magazines depending on caliber

AEK971 is being developed at Kovrov Machine building Plant (formerly known as Kovrov Machineguns Plant) by chief designer S.I.Koksharov.
Key feature of the AEK971 is gas driven, balanced action with rotating bolt barrel locking. Balancing mean that AEK971 gas drive has two gas chambers and two gas pistons. First gas piston is linked with a gas rod to the bolt carrier an moves as usual. Second gas piston is linked to the balancing msteel weight and moves in opposite (to main gas piston) direction. This design is implemented to eliminate 3 of 4 total impulses of the movement that affect rifle during the full-auto fire. 1st impulse rifle received when bullet moves along the barrel - this is recoil itself. Second impulse rifle received when heavy bolt carrier/bolt group moves along the receiver back and forth. Third impulse is received when bolt carrier/bolt group stops in the rear position and fourth - when this group stops in forward position after new cartridge is chambered. Synchronous and opposite movement of the balancing weight eliminates all except the recoil impulse, so rifle becomes far more stable during full-auto fire.
The gain of accuracy in full auto is whole 15-20%, when compared to AK-74 assault rifle in the same caliber. The newly adopted by Russian army AN-94 assault rifle has slight edge over the AEK974 only in short burst (2 rounds only) mode. In full-auto medium or long burst fire mode (3-5 or 7-10 rounds per burst) AEK974 wins hands down, being also some 0.5kg lighter than AN-94, simpler and cheaper to manufacture.
At the present time AEK971 in both 5.45x39mm and 7.62x39mm chambering is being tested by Russian army in some quantities (my sources said that at least one hundred of AEK971s in 7.62mm was acquired by Russian army for field testing).
AEK971 has folding metal butt stock with plastic coating (to protect shooter in extremely hot or cold conditions), plastic forearm and fire control grip, and uses standard AK-47 or AK-74 30rds magazines (depending on chambering). It also features safety switch/fire mode selector of different appearance (when compared to Kalashnikow design). Fire selector allows 2 modes of fire - single shots semi-auto and full auto. At some 800-900 rounds per second it's not impossible to manually control length of the fire bursts, and this weapon is more stable during the fire than ordinal design rifles, so 2 or 3 rounds mode is not implemented (at least, at this time).

"Groza" OC-14 (Russia)

Kaliber, mm: 9x39 SP-6, 7.62x39 M43
Action: Gas operated, rotating bolt with 2 lugs
Length, mm: overall: 700 barrel: 415
Sighting range,m: 700
Weigth, g: 3,200 (base config., unloaded)
Magazine, 20rds (9mm), 30rds AK-47 type (7.62mm)
Rate of fire, rds/min: 750

"Groza" (Thunder) OC-14 assult rifle/grenade launcher designed by CKIB SOO (Central Design Bureau of Sporting and Hunting Weapons), located in Tula, Russia, and manufactured by TOZ (Tula Weapons Plant, Russia).
This gun was initially designed for Russian Internal Affairs Ministry special forces as an assault rifle/grenade launcher kit, allowing quick in-field conversions to the following configuration:
- assault carbine (with short barrel)
- assault rifle (with longer barrel and post-type front handle)
- silenced assault rifle
- assault rifle/grenade launcher (for this conversion main fire control handle with triggerguard and triggergroup is removed, and a 40mm grenade launcher with new handle and trigger group is installed; This new trigger group has one trigger for both grenade launcher and rifle, and additional selector lever "grenade/rifle"
All parts necesary for this conversion supplied in one kit, along with carrying case
A 7.62mm version named "Groza-1" was developed for Army SpetzNaz. This version accepts AK-47 standart magazines and may be equipped with standart issue AK-74 bayonet.
Mounts for scopes or night vision devices are available.