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49-647: The HK21 is a German 7.62 mm general-purpose machine gun , developed in 1961 by small arms manufacturer Heckler & Koch and based on the G3 battle rifle . The weapon is in use with the armed forces of several Asian, African and Latin American countries. It was also license-manufactured by Fábrica de Braço de Prata in Portugal as the m/968 and in Mexico by SEDENA as the MG21 . In

98-483: A "Tropical" MP5-style handguard with ventilation slots. Quick-change barrel models have a four-position Picatinny Rail handguard (usually used with a vertical foregrip). It feeds from a 100-round HK21 belt box and uses either the American M13 or German DM6 disintegrating link belt. Vollmer only made 30 guns, 2 of which had quick-change barrels. General-purpose machine gun A general-purpose machine gun ( GPMG )

147-649: A 100-round sheet metal container, fastened to the bottom of the feed mechanism (as in the HK21A1). The ability to use G3 or STANAG (for HK23E) box or drum magazines is available with an optional feed module kit that consists of the bolt, recoil spring and belt feed module or magazine well. When employed in the belt-fed medium machine gun (fire support) role the HK21E provides a cook-off rate in excess of 1,000 rounds fired in quick succession. The shock-absorbing tripod weighs 10.5 kg (23.1 lb). A heavy machine gun variant of

196-418: A centerline, while the slots of the body incorporate a 5-, 10-, and 15-degree twisted helix design, which eliminates up to 99% of visible muzzle flash by having the flash break up at multiple locations and angles. The Noveske Rifleworks KX-3 is a flash suppressor intended for use on shorter barreled rifles and aids in reliability. The back pressure generated through this type of flash suppressor helps to cycle

245-451: A detachable bipod (mounted either in front of the feed mechanism or at the muzzle) and tripod and vehicle mounting points. The HK21 has close to a 48% parts interchangeability with the G3. The bolt features a spring-powered extractor and an anti-bounce device that prevents the bolt head from glancing off the barrel extension upon forward return of the locking assembly. The lever-type ejector system

294-424: A longer sight radius; the barrel extension was modified (the HK21E also received a longer barrel); a burst fire mode was incorporated into the trigger group as the fourth selector setting (3-round burst); a polymer barrel handle was added; space for a cleaning kit was added in the grip; the rear sight was modified with an adjustable drum; a bipod with a 3-position height adjustment and 30-degree tilt mechanisms replaced

343-407: A new modular family of machine guns that share the same receiver, trigger group and interchangeable barrels and feed units, consisting of: The "E" simply stands for "Export" model. They use STANAG rather than HK proprietary magazines and come with different optics than German military models. The E model is a thoroughly revised variant aimed to improve the reliability, efficiency and service life of

392-402: A proper and safe functioning parameters bandwidth Heckler & Koch offer a variety of locking pieces with different mass and shoulder angles. The angles are critical and determine the unlock timing and pressure curve progression as the locking pieces act in unison with the bolt head carrier. The HK21 uses a modified G3 receiver that has been extended to the front sight base and is equipped with

441-539: A rate of 850 rounds per minute , with lethality at ranges of more than 1,000 meters . The main feature of the MG 34 is that simply by changing its mount, sights and feed mechanism, the operator could radically transform its function: on its standard bipod it was a light machine gun ideal for infantry assaults; on a tripod it could serve as a sustained-fire medium machine gun ; mounting on aircraft or vehicles turned it into an air defence weapon, and it also served as

490-436: A rotary rear drum and hooded front post. The rear aperture sight is mechanically adjustable for both windage and elevation from 100 to 1,200 metres (109 to 1,312 yd) in 100-metre (109 yd) increments for 7.62×51mm NATO models or 100 to 1,000 metres (109 to 1,094 yd) in 100-metre (109 yd) increments for 5.56×45mm NATO models. By simply swapping out several components such as the barrel, bolt and feed plate unit,

539-399: Is advantageous for use against targets typically exposed to fire for a limited time span, like aircraft or targets minimizing their exposure by quickly moving from cover to cover. It was nicknamed " Hitler 's buzzsaw " by Allied troops, and alongside the MG 34 it inflicted heavy casualties on Allied soldiers on all European and North African fronts of World War II. Following the war

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588-641: Is an air-cooled , usually belt -fed machine gun that can be adapted flexibly to various tactical roles for light and medium machine guns . A GPMG typically features a quick-change barrel design calibered for various fully powered cartridges such as the 7.62×51mm NATO , 7.62×54mmR , 7.5×54mm French , 7.5×55mm Swiss and 7.92×57mm Mauser , and be configured for mounting to different stabilizing platforms from bipods and tripods to vehicles , aircraft , boats and fortifications , usually as an infantry support weapon or squad automatic weapon . The general-purpose machine gun (GPMG) originated with

637-406: Is contained in the trigger group housing and is actuated with every shot by the recoiling bolt. The weapon has a hammer striker and is fired from the closed bolt position, rare for general purpose machine guns. Firing from a closed bolt contributes to accurate fire, but is disadvantageous for heat dissipation. The trigger group, which is integrated with the pistol grip and hinged from the receiver,

686-448: Is equipped with a fire control selector switch (selector lever in the "E" or "1" position – semi-automatic fire, "F" or "20" – continuous fire mode) that doubles as a manual safety (rotating the lever into the "S" or "0" setting disables the trigger, weapon is considered "safe"). The HK21 has a free-floating, heavy, quick-change barrel fitted with a slotted flash suppressor . The firearm is equipped with an iron sight line that consist of

735-409: Is inserted into the bottom portion of the feed block (installed in place of the standard magazine well), below the barrel axis. As a result of this configuration (the bolt passes over the belt), the ammunition belt is aligned upside down compared to most other belt-fed weapons (that is, the links face downward). The feed mechanism is actuated by the reciprocating movement of the bolt; a curved cam slot on

784-643: The AKS-74U serve a dual-role as a gas expansion chamber helping the shortened weapon's gas system function properly. Military flash suppressors are designed to reduce the muzzle flash from the weapon to preserve the shooter's night vision , usually by diverting the incandescent gases to the sides, away from the line of sight of the shooter, and to secondarily reduce the flash visible to the enemy. Military forces engaging in night combat are still visible when firing, especially with night vision gear, and must move quickly after firing to avoid receiving return fire. Limiting

833-619: The Federal Police use a variant of the HK11 designated the Gewehr-8 (or G8 ). It is tapped for telescopic sights and has a quick-change barrel with a bipod that uses either a heavy match-grade bull-barrel or a heavy barrel for automatic fire. It was designed to use G3-type 10- or 20-round box magazines in the designated marksman role, but could also use a special 50-round drum magazine for sustained supporting or suppressing fire. The modified G8A1 adopted

882-590: The HK11A1 light machine gun. (optimized for magazine feed only). The HK11A1 proved more successful in export sales and was adopted by the Hellenic Army and several African and Asian armies. Both weapons, as in the original HK21, can be converted to chamber the 5.56×45mm NATO round by replacing the appropriate components. During the 1980s both the HK21A1 and HK11A1 were modernized based on user and testing feedback, resulting in

931-708: The Lee–Enfield , the rifle No. 5 Mk I variant, intended for use in the Pacific (the jungles of Malaya). More modern solutions tend to use a "basket" with several slits or holes cut in it, as seen on the M16 and other small-bore weapons. Cone-shaped flash eliminators are also evident on the ZB vzor 26 machine gun , and on the turret-mounted aircraft machine guns of British WWII heavy bombers, which were used mostly at night. Duckbill flash suppressors have upper and lower "prongs" and direct gases to

980-449: The M16 rifle used a unique flash suppressor sometimes called a flash or sound moderator for its 10-inch barrel. This device is 4.2 inches long and was designed primarily as a counterbalance measure, as the shorter barrel made the weapon unwieldy. This device reduced flash signature greatly and sound signature slightly, making the normally louder short barreled rifle sound like a longer barreled M16A1. Unlike conventional suppressors ,

1029-791: The MG 34 , designed in 1934 by Heinrich Vollmer of Mauser on the commission of Nazi Germany to circumvent the restrictions on machine guns imposed by the Treaty of Versailles . It was introduced into the Wehrmacht as an entirely new concept in automatic firepower, dubbed the Einheitsmaschinengewehr , meaning "universal machine gun" in German . In itself the MG 34 was an excellent weapon for its time: an air-cooled , recoil-operated machine gun that could run through belts of 7.92×57mm Mauser ammunition at

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1078-542: The coaxial machine gun on numerous German tanks . During World War II , the MG 34 was supplemented by a new GPMG, the MG 42 , although it remained in combat use. The MG 42 was more efficient and cheaper to manufacture, and more robust, as well as having an extremely high cyclic rate of fire of 1,200 to 1,500 rounds per minute. One of the Einheits Maschinengewehr GPMG roles was to provide low level anti-aircraft coverage. A high cyclic rate of fire

1127-461: The G3 and HK33 assault rifle bolts the HK21 bolt features an anti-bounce mechanism that prevents the bolt from bouncing off the barrel's breech surface. The "bolt head locking lever" is a spring-loaded claw mounted on the bolt carrier that grabs the bolt head as the bolt carrier group goes into battery. The lever essentially ratchets into place with friction, providing enough resistance to being re-opened that

1176-476: The German military ( Bundeswehr ) and the federal police ( Bundespolizei ) it is designated "G8". The HK21 is a selective fire roller-delayed blowback -operated firearm with a semi-rigid locking mechanism designed to retard the rearward movement of the bolt. This delay was achieved by artificially increasing the inertia of the bolt by using an angular, interposed transmission system, installed symmetrically to

1225-427: The HK21 chambered in .50 BMG /12.7×99mm NATO was proposed but never went into production. An aftermarket conversion of an HK21 general purpose machinegun into a belt-fed short carbine created by gunsmiths F. J. Vollmer & Company Inc. The barrel is 8.9 inches long, has an overall length of 21 inches, weighs about 11 lbs. unloaded, and has a rate of fire of 950 to 1,000 rounds per minute. Fixed barrel models have

1274-562: The M16A2 design makes the device function as a compensator. Both designs require indexing with a crush washer which increases flash signature. The Vortex Flash Hider is a design developed in 1984, with a patent secured in 1995. The Vortex is somewhat reminiscent of the original "three-prong flash hider" found on the original Vietnam-era M16 . However, the Vortex is more robust and makes use of four solid tines, which are equally spaced and angled 6° from

1323-539: The MG 1 and MG 3 ; the latter, as of 2023 , is still in production. Flash suppressor A flash suppressor is different from a muzzle brake , although they are typically mounted in the same position and sometimes confused with each other. While the former is intended to reduce visible flash, a muzzle brake is designed to reduce recoil inherent to large cartridges and typically does not reduce visible flash. Pre-20th century rifle designs tended to have longer barrels than modern rifles. A beneficial side effect of

1372-527: The White Sound Defense FOSSA-556. The U.S. military A2 muzzle device is technically a hybrid device: it has vents that are biased upwardly to reduce muzzle rise . Flash suppressors are seen as a "military" feature, and semi-automatic long guns with flash suppressors were defined as Military-Style Semi-Automatics in 1992, requiring a permit. Such weapons have since been prohibited. Flash suppressors were seen as "military" features and were on

1421-662: The XM177's moderator has no internal baffles and does not reduce the weapon's sound signature to subsonic levels; despite this, because it alters the sound level of the weapon, the United States Bureau of Alcohol, Tobacco, Firearms and Explosives has declared these moderators to be suppressors and regulates their civilian purchase in the United States. There are also devices referred to as hybrids that function as both flash suppressors and muzzle rise / recoil compensators , such as

1470-434: The amount of powder to what the length of a barrel can burn is one possible solution, but differences between individual cartridges mean that some cartridges will always have too much powder to be completely consumed, and the reduced powder load produces a lower projectile velocity. Muzzle flash can be controlled by using cartridges with a faster-burning propellant, so that the propellant gases will already have begun to cool by

1519-408: The bolt carrier and locking piece relative to the bolt head; the bolt head carrier travels backwards significantly faster than the bolt head, ensuring a safe drop of pressure within the barrel prior to extraction. Since extraction is carried-out under relatively high pressure, the barrel's chamber received a series of flutes designed to help free the bloated cartridge casing from the chamber wall. Like

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1568-413: The bolt carrier and recoil spring assembly, belt feed unit, buffer, barrel and trigger group. The redesigned belt feed mechanism transports the ammunition belt in two steps reducing stress on the feed and ammunition belt. Compared to the older HK21A1 and HK11A1, the modernized "Export" weapons also feature a longer barrel shroud, extended by 94 mm (3.7 in) towards the front, which also resulted in

1617-403: The bolt carrier does not rebound. The spring-powered claw extractor is also contained inside the bolt while the lever ejector is located inside the trigger housing (actuated by the recoiling bolt). The reliable functioning of roller-delayed blowback mechanisms is limited by specific ammunition and arm parameters like bullet weight, propellant charge, barrel length and amount of wear. For obtaining

1666-430: The bore axis, with two cylindrical rollers acting as transmission elements against a movable locking piece which drives the heavy bolt carrier. The two-piece bolt assembly consists of a bolt head, which contains the aforementioned rollers, and a supporting locking piece and bolt carrier. During the "unlocking" sequence, the bolt head receives the recoil impulse from the ignited cartridge and exerts rearward pressure against

1715-402: The bottom of the bolt engages an actuator in the feed mechanism, rotating the double sprockets and positioning a new round in the feed path. Simple conversion from belt to magazine feed is possible by installing an adapter in the feed block which enables the use of H&K's proprietary 20-round box magazine (from the G3 rifle) or a 50-round drum magazine . The German Army , German Navy and

1764-461: The early 1970s the HK21's design was simplified and the feed mechanism was modified. The machine gun's weight was increased, a carrying handle and a hooked buttstock with improved buffer mechanism were also added. The barrels were internally revised to polygonal rifling . Since then, the HK21 was offered in two main variants: the HK21A1 general-purpose machine gun (with a different belt feed mechanism) and

1813-427: The flash by rapidly cooling the gases as they leave the end of the barrel. Although the overall amount of burning propellant is unchanged, the density and temperature are greatly reduced, as is the brightness of the flash. A number of different flash suppressing designs have been used over the years. The simplest is a cone placed on the end of the barrel, which was used on the late-World War II jungle-combat versions of

1862-520: The improvements of the HK11A1 series and was only able to feed from magazines and drums. The GR-series were "sanitized" (i.e., having no serial numbers or identifying marks) Heckler & Koch weapons used by special operations forces. They differed from the stock weapons in that they had optical sights, no provisions for iron sights, and came standard in Woodland (-C suffix) or Desert (-S suffix) camouflage. In

1911-615: The introduction of various shorter-barreled rifles and carbines, the flash became a serious problem during night-time combat, as the flash would impair the shooter's night vision and would also make the shooter's position more apparent. Originally limited to "special purpose" roles, it was now expected that all infantry weapons with shorter barrels would experience this problem, and thereby be of limited use in low-light situations. Flash suppressors became common on late- World War II and later assault rifle designs, and are almost universal on these weapons today. Some designs such as those found on

1960-479: The list of federally defined features that could cause a rifle to be defined as illegal if the lower receiver was manufactured after the effective date of the Federal Assault Weapons Ban that went into effect in 1994 in the United States. This ban expired in 2004, although some states, such as California , Massachusetts , Maryland , New York , and New Jersey , have similar bans in place restricting

2009-465: The long barrel is that the propellant is completely burned before the bullet leaves the barrel, usually resulting only in a puff of smoke from the muzzle. However, if the same weapon's barrel is "cut down" (shortened), as is common in cavalry and jungle-combat adapted versions, the bullet would often leave the barrel before the powder was completely consumed, resulting in a bright flash from the muzzle. When barrel lengths were dramatically decreased with

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2058-628: The rifle. Noveske patterned this design on the muzzle brake found on the Soviet AKS-74U carbine, where it was explicitly used for this purpose. Essentially it is the cone-shaped suppressor of the AKS-74U within a chamber. Some other examples of cone-shaped hiders are found on the Bren machine gun, the .303 rifle No 5 Mk 1 " jungle carbine " and some models of the RPK and German MG3 . The XM177 Commando variant of

2107-420: The rollers, seated in recesses in the barrel extension. The rollers are driven inward against angled ramps of the barrel extension and interact with the wedge-shaped locking piece, projecting it backwards. Thus a chambering dependent (4:1 for 7.62×51mm NATO) or (3:1 for 5.56×45mm NATO) transmission ratio is maintained (as long as the rollers move on the inclined surfaces of the barrel extension and locking piece) of

2156-432: The sides. Early M60 machine guns and some Armalite AR-10 , Armalite AR-15 and early M16 models featured this type of flash suppressor. One disadvantage is that the prongs can become entangled with vines or other natural vegetation and objects in the field. "Birdcage type" flash suppressors still have prongs, but feature a ring on the front to prevent vegetation entanglement between the prongs. The closed bottom port of

2205-412: The simple folding bipod; the feed mechanism was modified to provide continuous feeding (by moving the belt in two stages, during both forward and rear movement of the bolt), a forward assist for silent loading was provided and the machine guns were adapted to use NATO -standard optical sight mounts. When employed in the light machine gun (infantry assault) role, the HK21E stores its ammunition belt in

2254-418: The time they exit the barrel, reducing flash intensities. Faster-burning powders, however, produce less projectile velocity, which reduces the accuracy, due to introducing a more parabolic bullet flight path in place of a "flat" trajectory, while also reducing the lethality of the weapon by reducing the distance of the projectile's penetration of the target. Flash suppressors reduce, or in some cases eliminate,

2303-594: The victorious Allied nations took an interest in the MG 34 and MG 42, influencing many post-war general-purpose machine guns, many still in use today. They lent design elements to the Belgian FN MAG and the American M60 , while spawning the Zastava M53, Swiss M51, and Austrian MG 74. The MG 42's qualities of firepower and usability meant that it became the foundation of an entire series of postwar machine guns, including

2352-584: The weapon can be quickly converted to the intermediate 7.62×39mm and 5.56×45mm NATO chamberings. The machine gun feeds from the left-hand side through a variety of disintegrating metallic link ammunition belt types: the American M13 linked belt, the German DM6 counterpart to the M13 or the German non-disintegrating metallic link DM1 belt. The ratcheting wheel feed unit was designed as an easily removable module that

2401-407: The weapon. For this the length of the receiver was increased by 25 mm (1.0 in) to provide additional recoil length for the bolt group. The recoil reduction improved accuracy of fire. Reinforcing bars were added to the receiver to provide additional strength and a guaranteed 60,000 rounds minimum service life. The bolt head, extractor and locking roller holder were completely redesigned as were

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