After the Second World War, a group of German designers worked at the CETME firm in Madrid, where they took part in the creation of a rifle operating on the principle of using the semi-recoil bolt (the scheme was developed by L. Forgrimmler, first implemented in the experimental StuG 45 (M) rifle). The company "NWM" (West Germany) showed interest in the development of this rifle and acquired the rights to it. But the leadership of the Bundeswehr decided to entrust the work on the creation of such a weapon to Heckler und Koch GmbH ("Heckler und Koch") in Oberndorf-Neckar, which retained part of the Mauser-Werke equipment. "Heckler und Koch" already in the 56th year released the first rifles under the NATO cartridge 7, 62x51 (note that in Spain the serial production of the new assault rifle was started only in the 58th year). In the 59th year, the Heckler und Koch rifle manufactured for the NATO cartridge 7, 62x51 under the designation G3 became standard for the Bundeswehr. Thus, the system, which originated in 1945 in Germany, “returned to its historical homeland” 15 years later. Some G3s had lightweight folding bipods and could serve as "ersatz" light machine guns.
Based on the G3 (NK91 - commercial designation), Heckler und Koch has developed one of the most extensive families of small arms. Today it is presented in four calibers - 5, 56 and 7, 62 mm light machine gun, assault rifle and carbine, 9 and 10 mm submachine gun. Due to more advanced technology, design and production organization, the G3 and its family significantly surpassed their Spanish prototypes in prevalence and popularity (the G3 and modifications were in service in 50 countries by the 90s). Within the family, they created a large series of machine guns of a single design. They did not find application in the Federal Republic of Germany, but they had some success in the foreign market.
Light machine gun NK21A1
The first, basic, model was the NK21, which was unified with the G3 and the rest of the 7.62 mm models of the family in some details. The machine gun was created to arm squads armed with G3 rifles. Its release is discontinued.
The operation of the automation is based on the use of the recoil of the semi-free shutter. The shutter is L-shaped. The return spring is located in the extended hollow end of the valve. The combat larva and the frame are mounted on the axis of the barrel bore. Long bearing surfaces on both sides of the frame move along the grooves of the receiver. Two rollers, which are installed on both sides of the combat larva, are held by the front inclined surface of the bolt stem, which acts as a "locking piece". This name is conditional, since in this system there is no locking of the barrel bore, but only a slowdown of the shutter retreat. The rollers fit into the grooves in the receiver. To eliminate the "jump" when sending the cartridge, the combat cylinder and the locking part are fixed on the frame using a clamping lever. Placing automation parts above the axis of the barrel bore makes it possible to increase the stability of the weapon when firing in bursts.
Light machine gun NK21A1
When there is a cartridge in the chamber, the rollers are in a dilated state and are held in the grooves of the receiver by a locking piece. During the shot, the pressure of the powder gases through the sleeve tries to move the bolt head back. Before the combat larva can move back, the rollers need to get out of the grooves and go back. The rollers, trying to converge, force the locking part and the frame to move back. The angle of the inclined surface at the locking part is such that the ratio of the speeds of movement of the combat head and the frame is 1: 4. Thus, while the rollers move to their original position, the frame traverses a distance 4 times greater than the combat head. In this case, the frame takes on most of the recoil energy. The clamping lever, when the frame moves back, releases the combat cylinder. When the shutter mirror moves back a little more than 1 millimeter, the rollers come out of the grooves of the receiver completely. After that, the bolt is thrown back by the force of the residual pressure, while the bolt carrier and the combat larva maintain an offset of 5 millimeters relative to each other. The bolt carrier compresses the return spring and cocks the hammer. The sleeve, which is held by the ejector, hits the reflector with the edge of the cap and is thrown through the receiver window to the right side. The bolt carrier reaches the shock absorber with its end part, and then returns forward under the action of the return spring. A cartridge is removed from the store with a combat larva and sent to the chamber. The cartridge engages with the ejector on the annular groove of the sleeve, the combat larva stops moving. The offset of 5 millimeters between the bolt carrier and the locking part is reduced to zero, while the rollers enter the grooves of the receiver. The combat larva is fixed with a clamping lever. The receiver is made of stamping steel. The guides are stamped on both sides. The cocking handle moves along a cutout made on the left side of the tubular casing, which is welded to the receiver above the barrel, and can be fixed using a special transverse cutout. The screw thread is applied to the muzzle of the barrel. A bushing is also installed there, designed to install a bushing for fire with blank cartridges or a retaining spring of a slotted compensator-flame arrester. For more reliable and smooth extraction of spent cartridges, the chamber has 12 longitudinal "Revelli grooves". Unlike the base rifle, the machine gun is equipped with a replaceable barrel with a handle for replacing it. The weight of the barrel is 1700 g. To detach the barrel, it must be turned by the handle, sliding it forward and pulled out to the right.
Power was supplied from a link tape with an open link. The tape was fed by two turning sprockets on the left. The receiver was equipped as follows. If the collapsible tape has a tip, then it passes from left to right through the feeder tray and is pulled in until the first cartridge reaches the lock. As the breech passes over the belt, the open side of the links must face upward. If the tape has no tip, the weapon must first be cocked. After the feed mechanism latch is released, the mechanism moves to the left. The first cartridge is placed in the sprockets of the feeder, they turn to the right. The feeder mechanism must then be returned to its original position. When lowering the reloading handle, the first cartridge is fed into the chamber from the tape. When firing, the moving bolt shifts the feeder roller to the right with its lower groove. The roller pushes the pusher, which turns the cam, which is put on one axis with the feeder sprockets. The sprockets turn, bringing the next cartridge to the chambering line. The weight of the cartridge box and tape for 100 cartridges is 3.6 kg.
The tape receiver, if necessary, can be removed and replaced with a magazine adapter inserted into the receiver and held in it by means of two latches. The device allows you to use a standard assault rifle magazine with a capacity of 20 rounds or a double-drum plastic magazine with a capacity of 80 rounds, which resembles the old MG34 magazine.
The trigger firing mechanism is similar to the trigger of the G3 rifle. The shot is fired from a closed bolt. USM is assembled in a separate case, attached to the receiver with a cotter pin. It is made in one piece with the trigger guard and pistol grip. The translator-safety flag is located above the pistol grip on the left side and has three positions: "safety" - upper, "single fire" - middle (the trigger moved a short distance), "continuous fire" - lower (the trigger moved completely). The spring-loaded sear has an oblong cutout, the protrusions of the trigger enter it. The spring seeks to move the sear above the trigger forward. At the same time, the sear is held by another spring. Until the bolt carrier takes the front extreme position, the shot cannot be fired. Only then does the safety sear release the trigger. After pressing the trigger, the sear turns downward, releasing the trigger from the combat cocking. The descent in the "safety" position is locked, the sear upward movement becomes impossible, and the lug will not be able to disengage from the trigger.
The diopter sight had a mechanism for introducing lateral corrections. Bringing the front sight back retained the ability of the base rifle to fire from the flash suppressor with feathered rifle grenades. The shape of the butt makes it possible to fire, holding it with the left hand, the butt has a shock absorber. The butt plate of the receiver, which has a plastic butt, when installed on machines, is replaced by a butt plate that does not have a butt.
The machine gun was adopted by the Portuguese army, some countries of Southeast Asia and Africa.
On the basis of the NK21 in the 73rd year, they created the NK21A1 machine gun. The main difference was the refusal to use the store. Meals - ribbon only. The tape receiver has been modernized - it can be folded down to thread the tape, which speeds up and simplifies this operation. The cartridge box with tape was attached to the bottom of the receiver. These machine guns are adopted in Mexico, Portugal, Greece and other countries. It was tested in the United States under the designation XM262, but was not adopted.
Modification of NK22 (NK21-7, 62x39) was made for cartridge 7, 62x39. It replaced the barrel, receiver and bolt, but the market for such a machine gun was able to find it. Modification of NK23 was performed under 5, 56x45 (American Ml93).
NK21E (caliber 7, 62 mm), NK23E (caliber 5, 56 mm) are the latest modification of the NK21A1 machine gun, created on the basis of operating experience. Several improvements applied to this weapon have led to the durability of the weapon and an increase in its effectiveness. The length of the receiver has been increased by 94 millimeters; sighting line and barrel are lengthened; reduced the length of the recoil of the moving parts of the automation. The mass increased by 500 g. USM received a mode of firing in fixed bursts, each of three shots, respectively, the fuse translator received another flag position. An improved quick-release barrel grip, a front holding grip, a winter detachable trigger and a trigger guard are installed. New sights are used that have settings of 100 - 1200 m (NK21E) or from 100 to 1000 m (NK23E) with the ability to adjust in direction and range and introduce lateral wind corrections. Other innovations were special devices that reduce the noise of the shutter operation, a set of cleaning accessories now in the pistol grip; barrel for firing blank cartridges and "winter descent" for firing in mittens. The cartridge box with the tape is installed on the lower grooves of the receiver in front of the trigger guard.
The system for feeding the tapes into the receiver has been modified in such a way that now the tape is fed in two stages, the power system began to work smoother, with less load on the tape itself and the receiver. During the movement of the bolt forward, the cartridge is removed from the tape. During the movement of the shutter in the opposite direction, in the second stage, the feed to the ramming line is completed. The NK21E machine gun received a barrel 560 mm longer. In the barrel of the NK23E machine gun, the rifling is made with a stroke length of 178 mm - for the NATO cartridge 5, 56x45, but there is a modification of the NK23E1 rifling stroke in which the rifling stroke is 305 mm (for the American cartridge).
Both machine guns were supplied with bipods having three fixed height settings, capable of turning 30 degrees horizontally in each direction. The bipod is secured in a T-shaped curved groove in the back or front of the barrel shroud. A characteristic feature of the bipod were concave supports, which allow them to be placed on the railing, side of the car, and the like. The NK21 machine gun was created as a single one, so its "descendants" can also be installed on the 1102 tripod machine, as well as other installations developed by Heckler und Koch (universal turret 2700, pivot 2400). The cushioned machine 1102 weighing 10.2 kilograms is equipped with horizontal and vertical guidance mechanisms, sliding hind legs. The machine gun can be equipped with an optical panoramic sight. However, given the power and effective firing range of the 5, 56 mm Ml93 cartridge or the NATO 5, 56 mm cartridge, the NK23E1 can be considered as a light machine gun with the ability to mount on the machine, and not as a single one. Among the export options, a variant was developed for the NATO cartridge 5, 56x45, and the Soviet 7, 62x39, which made the machine gun many-sided. The machine gun was altered by replacing the tape receiver guide, bolt and barrel.
Light machine gun NK23E
The barrel of the NK21 machine gun is slightly weighted, therefore, it does not withstand intensive fire. In Portugal, under license, NK21 was produced, in Greece - NK21A1 (ENK21A1), in Mexico - NK21E, in Italy, the Franchi company, but on the basis of NK23E, produced its own light machine gun LF / 23E with a polygonal barrel rifling. This machine gun is another example of close and long-standing cooperation between German and Italian military-industrial companies. Minor differences are due to the peculiarities of manufacturing technology in Italy. The length of the machine gun was 1030 millimeters. The chrome-plated barrel (the length of the rifling stroke is 178 mm) is designed for the SS109 cartridge of 5, 56 mm caliber (NATO 5, 56x45).
On the basis of the Heckler und Koch machine gun, they wanted to create a large-caliber single machine gun. The prototype NK25 was chambered for the.50 Browning cartridge and had a belt feed. Despite all the improvements, it did not work out.
Technical characteristics of the NK21E / NK23E light machine gun:
Cartridge - 7, 62x51 / 5, 56x45;
Machine gun weight with bipod - 9, 3/8, 75 kg;
Machine gun length - 1140/1030 mm;
Barrel length - 560/450 mm;
The number of grooves - 4;
Rifling stroke length - 305/178 mm;
Rate of fire - 800/750 rounds per minute;
Bullet muzzle velocity - 840/950 m / s.
