The Kalashnikov assault rifle, also known to the West as the AK-47 (Avtomat Kalashnikova - 47, Kalashnikov automatic rifle, model of 1947), and its derivatives, also known under the common name of AK, is the most prolific small arm of the 2nd half of the XX century. It had been and still is (in more or less modified form) manufactured in dozens of countries, and used in hundreds of countries and conflicts since its introduction. The total number of the AK-type rifles made worldwide during the last 60 years is estimated at 90+ millions. This is a true legendary weapon, known for its extreme ruggedness, simplicity of operation and maintenance, and unsurpassed reliability even in worst conditions possible. It is used not only as a military weapon, but also as a platform for numerous sporting civilian rifles and shotguns (see Saiga semiautomatic shotguns, for example). The AK is an amalgam of previously known features and solutions, combined in the most effective way. The effectiveness, however, depends on the criteria used to measure it, and the key criteria for any and every Soviet and Russian military arm are: Reliability, Simplicity of operation and maintenance, Suitability for mass production. There never was any significant demand for good ergonomics or superb accuracy, though. 

The true story of AK began late in 1942, when Soviet troops captured several specimen of the very new German MKb.42(H) machine carbine (assault rifle), along with some 7.92 Kurz ammunition. By mid-1943 the MKb.42(H) along with US-supplied M1 carbine were evaluated by Soviet experts, and it was decided on top level that similar weapons, firing the intermediate power cartridge, must be developed for Soviet army as soon as possible. The task of initial development of new ammunition was accomplished in rather short time. By November 1943 technical specifications for the 7.62x41mm cartridge, having bottlenecked, rimless case and firing 8-gram pointed bullet, were sent out to all Soviet small arms design bureaus and organizations. By the spring of 1944, there were at least ten designs of automatic weapons in the works (not counting semi-automatic carbines that resulted in adoption of SKS and bolt-action carbines that went nowhere). In mid-1944, trials commission selected the AS-44 assault rifle, designed by Sudaev, as the overall best, and ordered a limited production run for troops trials. Some AS-44 rifles were manufactured in spring of 1945, and these were evaluated by troops in summer of 1945, just after the Victory in Europe. Troops generally liked the AS-44, as it has longer effective range compared to PPSh-41 submachine gun, and provided better accuracy in semi-automatic fire. The problem was that AS-44 was overly heavy (more than 5 kg empty), and trials commission ordered next round of development and trials, which started early in 1946.

Enter Mikhail Kalashnikov, the young sergeant of Soviet tank forces, who, after being wounded in combat in 1942, designed a prototype submachine gun while on medical leave. His first weapon was rejected on the grounds of complexity, but the designer himself was assigned to the Red Armys Small Arms and Mortar Research & Proving ground (NIPSMVO) near the Moscow to continue his education and work on other weapons. Here Kalashnikov designed a semi-automatic carbine, heavily influenced by American M1 Garand rifle. This carbine, while not successful by itself, served as a starting point for the first Kalashnikovs assault rifle, provisionally known as AK No.1 or AK-46. In November of 1946 the AK-46 project was chosen for prototype manufacture along with 5 other projects (out of 16 submitted to commission), and Kalashnikov was sent to the city of Kovrov (also not far from the Moscow), to manufacture his weapon at the small arms factory there. The AK-46 was gas operated, rotary bolt weapon that utilized short-stroke gas piston above the barrel, and two-part receiver with separate trigger unit housing and dual controls (separate safety and fire selector switches on the left side of the trigger unit).
In December 1946 new assault rifles were tested at NIPSMVO range, with AS-44 being used as a control (its development has ceased earlier in 1946 due to untimely death of the Sudaev, who was severely ill by the 1945). As an initial result of these tests, the AK-46 was selected for further development by trials commission, with two more weapons selected for further evolution being rifles from designers Dementiev and Bulkin. The second round of trials, which included three weapons (AK-46 by Kalashnikov, AB-46 by Bulkin and AD by Dementiev), resulted in rejection of the improved AK-46, which was inferior to other rivals in many aspects. Despite that failure, Kalashnikov, using his contacts and support from some member of trials commission (whom he knew from his earlier work at NIPSMVO in 1943-46) pursued the head of the trials commission to review the results, and finally got a green light to continue his development for next round of trials. Following the technical failure of the AK-46, Kalashnikov and his companion designer Zaitsev (who was a staff weapons designer at Kovrov plant) decided to completely rework the design, using successful technical solutions borrowed from various weapons, including direct competitors. For example, the long-stroke gas piston, attached to the bolt carrier, along with captive return spring assembly and receiver cover were apparently inspired by Bulkins AB-46 rifle; the idea of large clearances between bolt group and receiver walls, with minimum friction surfaces, was inspired by the Sudaevs AS-44, the safety / dust cover lever was copied from Browning designed Remington model 8 hunting rifle etc.
It must be noted here, that such copying and borrowing of ideas was actually encouraged by the trials commission (and the whole Soviet ideology), as all intellectual property in USSR was considered to be property of the people, or the state. Thus, any state-owned intellectual property could (and must) have been used to the benefit of the people / the state by anyone. And creating a new, most effective assault rifle for the victorious Soviet army was certainly on the top of the list of things, beneficial for the Soviet state at the time.

After extensive tests, conducted in December 1947 - January 1948, which included slightly improved Dementiev KB-P-410, Bulkin TKB-415 and all-new Kalashnikov AK-47 rifles, results were somewhat inconclusive. The AK-47 was found to be most durable and reliable out of three contestants, but it also dragged behind the other two in the accuracy department, especially in full automatic (which was, and still is considered the primary mode of fire for assault rifle in Russia). In fact, the only weapon that fulfilled accuracy requirements was the Bulkin AB-47 / TKB-415, but it had certain problems with parts durability. After lengthy discussion, trials commission finally decided that the better is the enemy of the good, and it is advisable to have not-so accurate but reliable weapon now, rather than to wait indefinitely for accurate-and -reliable weapon in the future. This decision ultimately lead commission to recommend AK-47 for troops trials in November, 1947. It was decided that the production of the new weapon must be commenced at Izhevsk arms plant (now Izhevsk Machine building Plant or IzhMash in short). Kalashnikov has moved from Kovrov to Izhevsk to help with production of the new weapon, which commenced in mid-1948. Official adoption followed late in 1949, with standard nomenclature being 7.62mm avtomat Kalashnikova AK (7.62mm automatic carbine Kalashnikov). At the same time, a folding buttstock version was adopted for airborne units use, as 7.62mm avtomat Kalashnikova skladnoy AKS (7.62mm automatic carbine Kalashnikov, folding).
It must be noted that the original design of the receiver, which was assembled from stamped steel box with large machined steel insert pinned at the front, caused a lot of troubles at factory. The technology (equipment and labor) level of the time resulted in extremely high percentage of rejected receivers due to misformed walls, improper pinning of parts, bad geometry etc. After critical revision of the process at the factory it was calculated that it will be more economically feasible to return to the old-school machined receivers. New, machined receiver was designed by one of factorys staff designers, and after approval by military, it was put into production at IzhMash in 1951, under the same basic designation. 

Through the following years, design of AK incorporated many minor changes and updates, but it was the experimental Korobov TKB-517 assault rifle (tested by Soviet army in mid-fifties) that spurred further development of AK. The Korobov TKB-517 assault rifle was a great deal lighter than AK, about 1/3 cheaper to manufacture, and significantly more accurate in full automatic fire. This lead the Soviet army to issue new requirements for a lighter and more effective assault rifle, which were formulated in 1955. These requirements were also complemented by requirement for a companion squad automatic / light support weapon (light machine gun in Russian nomenclature). Trials for new weapons were held in 1957-58. Kalashnikov team from Izhevsk submitted an improved AK with new type of stamped receiver and other minor improvements, which competed against a number of weapons from other design teams from the Kovrov and Tula. In technical terms, the Kalashnikov entry fared about average in these trials, with certain rival weapons proving to be more combat-effective and less expensive to make. The trials commission, however, decided again that the better is the enemy of the good, and recommended the improved AK for adoption due to its proven performance and familiarity to the industry and troops. It was officially adopted in 1959 as the AKM ( Avtomat Kalashnikova Modernizirovannyj - Kalashnikov Automatic rifle, Modified) along with companion RPK squad automatic weapon / light machine gun. 

The key changes in AKM, as compared to AK, were the introduction of the stamped steel receiver instead of the milled one, and improved trigger/hammer unit, with added hammer release delay device (often incorrectly referred as a rate reducer). Other changes were the redesigned, slightly raised buttstock and the pistol grip, and the addition of the removable muzzle flip compensator. This spoon-like compensator is screwed onto the muzzle and utilized the muzzle blast to reduce muzzle climb during the automatic fire. The compensator could be replaced by the screw-on "PBS-1 noiseless firing device", generally known as a silencer. This silencer requires a special, sub-sonic ammunition with heavier bullets to be used. Another change from AK to AKM was a slightly improved rear sight, with settings from 100 to 1000 (instead of the 800 on AK) meters. Both 800 and 1000 meters, however, are way too optimistic for any practical use, since the effective fire is limited roughly to 300-400 meters, if not less.

In the 1974, Soviet Army officially adopted the 5.45mm ammunition and the appropriately chambered AK-74 assault rifle as its new standard shoulder arm. The AKM, however, was never officially declared obsolete and removed from service, and is still in Russian army stocks. Some non-infantry units of the Russian Army are still armed with 1960s vintage AKM assault rifles. Theres also an increasing interest in the 7.62mm weapons since many troops were disappointed by the effectiveness of the 5.45mm ammo during the local conflicts in the 1990s. Some Russian special forces troops (mostly police and Internal Affairs Ministry), currently operating in Chechnya, are using the venerable 7.62mm AKM rifles.

The AK and AKM rifles were widely exported to the pro-Soviet countries and regimes all around the world. Manufacturing licenses along with all necessary technical data packages were transferred (for free or at nominal fee) to many Warsaw Pact countries (Albania, Bulgaria, China, East Germany, Hungary, North Korea, Poland, Romania, Yugoslavia). Certain non-communist, but friendly countries, such as Egypt, Finland and Iraq, also received manufacturing licenses.

At the present time, despite the world-wide proliferation of the small-bore (5.56 / 5.45mm) weapons, many companies still manufacture 7.62mm assault rifles for military or police use (for example, theres an AK-103, made in limited numbers by the IZHMASH in Russia). Also, production of the semi-automatic only civilian AK derivatives is continued in many countries, including Russia, Bulgaria, Romania, China and others.

Technical description for the AKM assault rifle:
The AKM is a gas operated, selective fire assault rifle.

The gas operated action has a massive bolt carrier with a permanently attached long stroke gas piston. The gas chamber is located above the barrel. The bolt carrier rides on the two rails, formed on the receiver walls, with the significant clearances between the moving and stationary parts, which allows the gun to operate even when its interior is severely fouled with sand or mud. The rotating bolt has two massive lugs that lock into the receiver. Bolt is so designed that on the unlocking rotation it also makes a primary extraction movement to the fired case. This results in very positive and reliable extraction even with dirty chamber and cases. The rotation of the bolt is ensured by the curved cam track, machined in the bolt carrier, and by the appropriate stud on the bolt itself. The return spring and a spring guide are located behind the gas piston and are partially hidden in its hollow rear part when bolt is in battery. The return spring base also serves as a receiver cover lock. The cocking handle is permanently attached to the bolt carrier (in fact, it forms a single machined steel unit with carrier), and does reciprocate when gun is fired.

The receiver of the AKM is made from the stamped sheet steel, with machined steel inserts riveted into the place where required. Earliest AK-47 receivers were also made from the stamped and machined parts, riveted together, but this soon proved to be unsatisfactory, and most of the AK (made between 1951 and 1959) rifles were made with completely machined receivers. The receiver cover is a stamped sheet metal part, with stamped strengthening ribs found on the AKM covers.

The relatively simple trigger/hammer mechanism is loosely based on the 1900s period Browning deigns (much like the most other modern assault rifles), and features a hammer with two sears - one main, mounted on the trigger extension, and one for the semi-automatic fire, that intercepts the hammer in the cocking position after the shot is fired and until the trigger is released. Additional auto sear is used to release the hammer in full auto mode. The AKM trigger unit also featured a hammer release delay device, which is served to delay the hammer release in the full auto fire by few microseconds. This does not affects the cyclic rate of fire, but allows the bolt group to settle in the forwardmost position after returning into the battery. The combined safety - fire selector switch of distinctive shape is located on the right side of the receiver. In the "Safe" position (topmost) it locks the bolt group and the trigger, and also served as a dust cover. The middle position is for automatic fire, and the bottom position is for single shots. The safety / fire selector switch is considered by many as the main drawback of the whole AK design, which is not cured in the most of derivatives until now. It is slow, uncomfortable and sometimes stiff to operate (especially when wearing gloves or mittens), and, when actuated, produces a loud and distinctive click. Theres no bolt stop device, and the bolt always goes forward when the last shot from the magazine is fired.

AKM is fed from the 30 rounds, stamped steel magazines of heavy, but robust design. Early AK magazines were of slab-sided design, but the more common AKM magazines featured additional stamped ribs on the sides. Positive magazine catch is located just ahead of the trigger guard and solidly locks the magazine into the place. Insertion and the removal of the magazine requires slight rotation of the magazine around its front top corner, that has a solid locking lug. If available and required, a 40 round box magazines of similar design, or the 75 rounds drums (both from the RPK light machine gun) can be used. Late in production plastic magazines of the distinctive reddish color were introduced.

AKM rifles were issued with wooden stocks and pistol handles. Late production AKM rifles had a plastic pistol grip instead of wooden one. The wooden buttstock has a steel buttplate with mousetrap cover, that covers the accessory container in the butt. The AK buttstock are more swept-down than the AKM ones. The folding stock version had been developed for the airborne troops and its had an underfolding steel shoulder stock. These modifications of the AK and AKM were designated the AKS and AKMS, respectively. AK were issued with the detachable knife-bayonets, and the AKM introduced a new pattern of the shorter,  multipurpose knife-bayonet, which can be used in conjunction with its sheath to form a wire-cutter. All AK and AKM rifles were issued with the canvas carrying slings.

The sights of the AKM consist of the hooded front post and the U-notch open rear. Sights are graduated from 100 to 1000 (800 on AK) meters, with an additional "fixed" battle setting that can be used for all ranges up to 300 meters. 

AKM rifles also can be fitted with the 40mm GP-25 grenade launchers, that are mounted under the forend and the barrel. Grenade launchers had its own sights on the left side of the unit.

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