MG 3 machine gun
The Rheinmetall MG 3 is a German general-purpose machine gun chambered for the 7.62×51mm NATO cartridge. Manufactured by Rheinmetall for the Bundeswehr, designed and derived from the World War II era MG 42 that fired the 7.92×57mm Mauser round.
The MG 3 was standardized in the late 1950s and adopted into service with the newly formed Bundeswehr, where it continues to serve to this day as a squad support weapon and a vehicle-mounted machine gun.
The MG 3 and its derivatives have also been acquired by the armed forces of over 40 countries. Production rights to the machine gun were purchased by Italy, Greece, Iran Pakistan, Sudan, Spain, and Turkey.
History
At the end of World War II, the original technical drawings and data for the 7.92×57mm Mauser–chambered MG 42 were captured by the Soviets. These would later be taken to Czechoslovakia and Yugoslavia. Rheinmetall had to reverse engineer the first postwar machine guns from an original MG 42 machine gun.Production of the first postwar variant of the MG 42 chambered for 7.62×51mm NATO ammunition was launched in 1958 at the Rheinmetall arms factory as requested by the Bundeswehr. Shortly thereafter, the machine gun was modified, receiving a chrome-lined barrel and sights properly calibrated for the new round; this model would be named the MG 1A1.
The MG 1A2 is a further development of the MG 1A1, which has a heavier bolt, and a new friction ring buffer made suitable for using the heavier bolt. The MG 1A2 added new bolt-bounce preventing bolt catches to the action to resolve the ammunition ignition timing sensitivity of the preceding variants and was adapted to use both the standard German non-disintegrating Patronengurt DM1 ammunition belt and the American M13 disintegrating belt. The MG 1A3 features further improvements to the muzzle device, bipod and bolt.
Simultaneously, wartime 7.92×57mm Mauser chambered MG 42 machine guns that remained in service were converted to the standard 7.62×51mm NATO chambering and designated MG 2.
In 1968, the MG 3 was introduced and entered production. Compared to the MG 1A3, the MG 3 features an improved feeding mechanism with a belt retaining pawl to hold the belt up to the gun when the top cover plate is lifted, an added anti-aircraft sight and a new ammunition box. MG 3s were produced for Germany and for export customers by Rheinmetall until 1979. The preceding non–MG 3 variant machine guns in the Bundeswehr inventory were gradually converted to the MG 3 standard. Some additional production of the MG 3 in Germany was carried out by Heckler & Koch. The MG 3 and its variants all share a high level of parts interchangeability with the original MG 42.
MG 3s continue to be produced in Turkey and Pakistan. In 2019 there were plans in Germany to produce several thousand new MG 3 receivers to keep using vehicle mounted MG 3s in the low level anti-aircraft and turret mounted roles in the near future.
Deployment
The MG 3 is still used as the standard secondary weapon of most modern German armoured fighting vehicle designs, as a primary weapon on light/non-armoured vehicles and as an infantry weapon on light bipods as well as different tripods. Since 2015, the German Armed Forces have supplemented the MG 3 with the Heckler & Koch MG5.Reliability
In 1974, the US Army tested German made MG 3s alongside eight other contemporary GPMG designs to replace the then-in-service M219 Tank Machine Gun, which was considered unacceptably unreliable by the US Army. The MG 3 had worse results in mean rounds between failure, mean rounds between stoppage, cookoff rate, and accuracy than the M60 and FN MAG. The only categories in which the MG 3 outperformed both the M60 and FN MAG were in ease of training, ease of changing barrels, and safety. The MG 3 was overall sixth of nine candidates in an unweighted ranking, and it was considered that no reasonable combination of attribute rankings existed in which it would be the winner of the contest.Operational use
The German military instructs that sustained fire must be avoided at all costs. In the bipod mounted light machine gun role, MG 3 users are trained to fire short bursts of three to five rounds and strive to optimize their aim between bursts fired in succession. In the tripod mounted medium machine gun role, MG 3 users are trained to fire both short bursts and longer bursts of 20 to 30 rounds and strive to optimize their aim between successive bursts. The Bundeswehr trains soldiers to replace the barrel of the MG 3 after 150 live rounds after sustained heavy fire, with a new, cooler one; only once the barrel is hand-warm can a barrel be reused. Replacing the barrel is a simple procedure on the MG 3. Non-observance of this technical limitation renders the barrel prematurely unusable. Care must be taken when replacing the barrel as after extended cyclical fire, the barrel can be dangerously hot, potentially approaching white hot. The machine gun crew member responsible for a hot barrel change is issued protective asbestos gloves or a cloth to prevent burns to the hands. The effective rate of fire is about 250 rounds per minute. Some other machineguns have thermally insulated grips attached to their quick-change barrel, at least going back to the ZB vz. 26 design of 1926.Design details
The MG 3 has an automatic-only trigger mechanism and a cross-bolt safety in the form of a button that is operated by the shooting hand. The MG 3 fires from an open bolt. The cyclic rate can be altered by installing different bolts and recoil springs. A heavier bolt uses more recoil energy to overcome inertia, thus slowing the action. On MG 3 machine guns, two types of bolts are available, with standard weight for the standard 1,000–1,200 rounds per minute cyclic rate of fire and with extra weight for a slower 800–950 rounds per minute cyclic rate of fire. Those bolts also are used along with different return springs.Operating mechanism
The MG 3 is an automatic, air-cooled, belt-fed short recoil–operated firearm. It features a roller locked bolt mechanism that consists of the bolt head, a pair of rollers, the striker sleeve, bolt body and return spring. The bolt is locked securely by a wedge-shaped striker sleeve, which forces two cylindrical rollers contained in the bolt head outward, and into corresponding recesses in the extension of the breech of the barrel. On firing, both the barrel and barrel extension recoil to the rear. The resulting impact moves the carrier to the rear, withdrawing the wedge and both rollers as they are cammed inward and out of their sockets by fixed cams, unlocking the bolt head. The bolt carrier and bolt then continue to the rear together guided by fixed guides while the barrel and barrel extension return to battery. Upon return of the bolt forward, the impact of the rollers against the camming surfaces on the breech carry the rollers from their seats, and, together with the surfaces on the striker sleeve, force the rollers outward, locking the bolt head into the barrel extension and ensuring a complete lock. The bolt also houses a spring-loaded casing extractor and ejector. Ejection is carried out when the ejector strikes the buffer head, sending a push forward through the ejector bar, which hits the ejector pin. This pin pushes the top of the base of the cartridge, which is still held by the extractor at the base, causing the empty casing to rotate and eject downward through the ejection chute.Barrel
The MG 3 has a quick-change, chrome-lined barrel with four right-hand grooves and a rifling twist rate of 1 in 305 mm and weighs. Alternatively, MG 3 barrels can also have polygonal rifling. The barrel is integrated with the barrel breech. During sustained firing, there is a need for the barrel to be changed and this is how they are swapped: The gun is cocked and the barrel catch on the right of the barrel shroud is swung forward. Then, the breech end of the hot barrel swings out and can be removed by elevating or twisting the gun. A fresh barrel would be inserted through the barrel catch and the muzzle bearing. When the catch is rotated back, the barrel is locked and the machine gun can resume firing. Both the receiver housing and ventilated barrel casing are made from pressed sheet steel. The machine gun crew member responsible for a hot barrel change is issued protective asbestos gloves to prevent getting burned. A muzzle device is mounted at the end of the barrel and it acts as a flash suppressor, muzzle brake and recoil booster.Feeding system
The MG 3 feeds from the left side through a feed block using a metal 50-round drum that uses a non-disintegrating metallic-link DM1 belts ammunition belts or disintegrating-link M13 or DM6 belts.In the light machine gun role, the MG 3 is deployed with a 100-round belt fitted inside a synthetic ammunition drum developed by Heckler & Koch that is latched on to the left side of the receiver. The rear wall of the drum is transparent and serves as a visual indicator for the amount of ammunition available. The feed system operates through a feed arm that is housed in the feed cover. Two feed pawls are linked to the front end of the arm by an intermediate link and move in opposite directions, moving the belt in two stages as the bolt moves back and forward during firing.
DM1 belts are intended for multiple reuse and in terms of design are based on and derived from the last version of the Gurt 34/41-belt family used in World War II in MG 34 and MG 42 machine guns. DM1 belts are preloaded at ammunition factories in 50-round connectable belt lengths and can be linked to any length necessary. Spent cartridge cases are ejected downwards, and the emptied links are transported to the right.
Alternatively, the MG 3 can also be fed by disintegrating metal M13 link belts used by many NATO member states. M13 links are also used on the Dillon M134D Minigun, M60, FN MAG, HK21 and MG5 machine guns among others. The disintegrating metal belt is fed from the left side. Ejection of empty M13 links is to the right side, and spent cartridge cases are ejected downwards. The inexpensive M13 links are considered disposable.
Both belt types are of the push-through type and use a metal lip that is arrested in the rim of the cartridges to correctly position and fix the cartridges in place. The feeding system is based on the direct push-through of the cartridge out of the belt link into the gun's chamber. Feed is performed in two steps by a pawl-type feeding mechanism that continues to move the belt during both the rearward and forward cycles of the reciprocating bolt, producing a smooth belt flow.
For field use, there are several ammunition containers available. The Gurttrommel contains a 50-round DM1 or DM60 belt. The Gurttrommel is not a true magazine but holds a curled 50-round belt preventing it from snagging, twisting and getting stuck during mobile assaults. The steel DM2 ammunition box contains a 250-round DM1 belt and the smaller plastic DM40004 ammunition box contains a 100-round DM1 belt or a 120-round DM60/M13 belt. The German military tends to use non-disintegrating DM1 belts for general use and disintegrating DM60/M13 belts in vehicle or aircraft fixed MG 3 mountings that allow for collecting the ejected link pieces for reuse.