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Royal Marines Light Machine Gun

FN Minimi

L110A1Light Machine Gun5.56 x 45 mmbelt or magazine.

The Minimi (short for French: Mini Mitrailleuse; "mini machine gun") is a Belgian 5.56mm light machine gun developed by Fabrique Nationale (FN) in Herstal by Ernest Vervier. First introduced in 1974, it has entered service with the armed forces of several countries. The weapon is currently manufactured at the FN facility in Herstal as well as being licence-built in Australia, Greece and the USA by FN Manufacturing LLC.

The Minimi is a light machine gun firing from an open bolt. The weapon is primarily chambered for 5.56x45mm NATO, though a 7.62x51mm NATO variant exists. It is an air-cooled weapon, capable of fully automatic fire only. It can be belt fed or fired from a magazine.

The Minimi is configured in several variants, the Standard model as a platoon or squad support weapon, the Para version for paratroopers and the Vehicle model as secondary armament for fighting vehicles.

M249 Minimi
An early M249 version of the Minimi

Design details

Operating mechanism

The Minimi uses a gas-actuated long-stroke piston system. The barrel is locked with a rotary bolt, equipped with two massive locking lugs, forced into battery by a helical camming guide in the bolt carrier. Upon firing, the piston is forced to the rear by expanding propellant gases bled through a port in the barrel near the muzzle end. The piston rod acts against the bolt carrier, which begins its rearward motion guided on two rails welded to the receiver walls, while the bolt itself remains locked. This sequence provides a slight delay that ensures chamber pressure has dropped to a safe level by the time a cam in the bolt carrier rotates and unlocks the bolt, increasing extraction reliability as the empty cartridge casing has had the time to cool down and contract, exerting less friction against the chamber walls.

The Minimi fires from an open bolt, which reduces the danger of a round cooking off after extended periods of continuous fire, since a cartridge is only momentarily introduced into the chamber prior to ignition, and the movement of the bolt and bolt carrier forces air through the chamber and barrel after each shot, ventilating the barrel and removing heat. Gas escaping the gas cylinder is directed upward, avoiding kicking up dust and debris that would reveal the shooter's position.

Features

The Minimi has a manually adjustable gas valve with two positions, normal and adverse. The adverse setting increases the cyclic rate of fire from 700–850 rounds per minute to 950–1,150 rounds per minute and is used only in extreme environmental conditions or when heavy fouling is present in the weapon's gas tube. The spring extractor is located inside the bolt, while the tilting lever ejector is contained inside the receiver housing. Spent casings are removed through a port located at the bottom of the right side of the receiver, protected from debris with a spring-loaded dust cover.

The Minimi is striker-fired and the bolt carrier functions as the striker mechanism. The Minimi has a push-button type manual safety installed in the trigger housing, above the pistol grip. In the "weapon safe" position, it disables the sear mechanism; pushing the button to the right side exposes a red-colored rim on the left side of the firearm and indicates the weapon is ready to fire. The black polymer pistol grip was initially copied directly from the FAL and FNC rifles, but is currently manufactured with a modified grip with lateral grooves, installed at a smaller angle to the receiver.

Minimi Para with telescopic sight
The Minimi Para with a telescopic sight, spare barrel and ammunition pouches.

The Minimi features a welded receiver made from stamped steel. Both the standard and Para variants are equipped with a fixed, folding bipod mounted to the gas tube and stowed under the handguard. The bipod can be adjusted in height and each leg has three height settings. The bipod also offers a 15° range of rotation to either side. With the bipod fully extended, the bore axis is elevated to a height of 465 mm (18.3 in). The Minimi can also be fired from the Belgian FN360° tripod or the American M122 mount using an M60 pintle. The vehicle-mounted Minimi is fitted with an electrically-powered trigger that enables it to be fired remotely from within an armored fighting vehicle.

The standard light machine gun version has a 465 mm (18.3 in) barrel and a skeletonized aluminum stock with a folding wire shoulder strap. The shortened Para model has a 349 mm (13.7 in) barrel and a collapsible metal stock, while the vehicle-mounted model has a 465 mm (18.3 in) barrel but does not have a stock or iron sights. All models can alternatively be fitted with a fixed synthetic stock, the same used on the M249, which contains a hydraulic buffer that contributes to stabilizing the rate of fire and reducing recoil forces.

Feeding

The weapon is fed from the left-hand side by disintegrating-link M27 ammunition belts (a miniaturized version of the 7.62mm M13 belt), from either an unsupported loose belt, enclosed in a polymer ammunition box with a 200-round capacity attached to the base of the receiver, or from detachable STANAG magazines, used in other NATO 5.56mm assault rifles such as the M16 and FNC. Magazine feeding is used only as an auxiliary measure, when belted ammunition has been exhausted. The ammunition belt is introduced into the feed tray, magazines are seated inside the magazine port at a 45° angle, located beneath the feed tray port. When a belt is placed in the feed tray it covers the magazine port. Likewise, a magazine inserted into the magazine well will prevent the simultaneous insertion of a belt. The magazine port, when not in use, is closed with an L-shaped hinged flap equipped with a tooth, which engages a corresponding opening in the magazine and serves as a magazine release. This feature was developed by FN's Maurice V. Bourlet and allows the Minimi to be instantly changed from belt feed to magazine feed without any modification.

The pawl-type feeding mechanism is modeled on the system used in the MAG general purpose machine gun, which borrows from the World War II-era MG 42. The belt is moved in two stages during both the forward and rearward movement of the reciprocating bolt carrier, which provides for a smooth and continuous feeding cycle. The feeding mechanism top cover features a device that indicates the presence of a cartridge in the feed path.

Lifting the feed tray cover
Lifting the feed tray cover reveals the rotary bolt locking mechanism.

Barrel

The barrels used in the Minimi have an increased heat capacity for sustained fire, feature a chrome-lined rifled bore (six right-hand grooves) and are manufactured in two versions: with a 178 mm (1:7 in) twist rate used to stabilize the heavier Belgian 5.56×45mm SS109 projectile, or a 305 mm (1:12 in) twist for use with American M193 ammunition. The barrels have a quick-change capability; a lever is provided on the left side of the weapon that releases the barrel from its trunnion. A carrying handle is also fixed to the barrel and assists in the barrel change process. A trained soldier can perform a barrel change and ready the weapon for aimed fire in 6–7 seconds. Early versions of the Minimi had a flash suppressor with side ports as seen on the FNC, CAL and FAL rifles; new production guns have a shorter, cone-shaped slotted flash suppressor.

 

Sights

Both the standard and Para models come with a rear sight, adjustable for windage and elevation, that provides a peep aperture for ranges from 300 to 1000 m in 100 m increments. The hooded front sight is installed in a post on the gas block and is also adjustable for elevation and windage. Early models of the Minimi had the rear sight mounted forward of the feed cover and the front post secured to the barrel, closer to the muzzle end. An adapter can also be used that allows the use of standard NATO night and day sights.

Accessories

Standard equipment supplied with the Minimi consists of three ammunition boxes, a cleaning kit stored inside the forearm, lubricant bottle, sling and blank-firing adaptor.

Action

The choice between bolt-action and semi-automatic (more commonly recoil or gas operation) is usually determined by specific requirements of the sniper's role as envisioned in a particular organization, with each design having advantages and disadvantages. For a given cartridge, a bolt-action rifle is cheaper to build and maintain, more reliable and accurate, and lighter, due to fewer moving parts in the mechanism. In addition, the lack of an external magazine allows for more versatile fire-positioning, and the absence of uncontrolled automatic cartridge case ejection helped to avoid revealing the firer's position. Semi-automatic weapons can serve both as battle rifle and sniper rifle, and allow for a greater rate (and hence volume) of fire. As such rifles may be modified service rifles, an additional benefit can be commonality of operation with the issued infantry rifle. A bolt action is most commonly used in both military and police roles due to its higher accuracy and ease of maintenance. Anti-materiel applications such as mine clearing and special forces operations tend to use semi-automatics. A Marine manually extracts an empty cartridge and chambers a new 7.62x51mm round in his bolt-action M40A3 sniper rifle. The bolt handle is held in the shooter's hand and is not visible in this photo.

A designated marksman rifle (DMR) is less specialized than a typical military sniper rifle, often only intended to extend the range of a group of soldiers. Therefore, when a semi-automatic action is used it is due to its ability to cross over into roles similar to the roles of standard issue weapons. There may also be additional logistical advantages if the DMR uses the same ammunition as the more common standard issue weapons. These rifles enable a higher volume of fire, but sacrifice some long range accuracy. They are frequently built from existing selective fire battle rifles or assault rifles, often simply by adding a telescopic sight and adjustable stock.

A police semi-automatic sniper rifle may be used in situations that require a single sniper to engage multiple targets in quick succession, and military semi-automatics such as the M110 SASS are used in similar "target-rich" environments.

Cartridge

In a military setting, logistical concerns are the primary determinant of the cartridge used, so sniper rifles are usually limited to rifle cartridges commonly used by the military force employing the rifle. Since large national militaries generally change slowly, military rifle ammunition is frequently battle-tested and well-studied by ammunition and firearms experts. Consequently, police forces tend to follow military practices in choosing a sniper rifle cartridge instead of trying to break new ground with less-perfected (but possibly better) ammunition.

Before the introduction of the standard 7.62x51mm_NATO cartridge in the 1950s, standard military cartridges were the .30-06 Springfield or 7.62x63mm (United States), .303 British (7.7x56mmR) (United Kingdom) and 7.92x57mm (8mm Mauser) (Germany). The .30-06 Springfield continued in service with U.S. Marine Corps snipers during the Vietnam War in the 1970s, well after general adoption of the 7.62x51mm. At the present time, in both the Western world and within NATO, 7.62x51mm is currently the primary cartridge of choice for military and police sniper rifles.

Worldwide, the trend is similar. The preferred sniper cartridge in Russia is another .30 calibre military cartridge, the 7.62 x 54 mm R, which has similar performance to the 7.62x51mm. This cartridge was introduced in 1891, and both Russian sniper rifles of the modern era, the Mosin-Nagant and the Dragunov sniper rifle, are chambered for it.

Certain commercial cartridges designed with only performance in mind, without the logistical constraints of most armies, have also gained popularity in the 1990s. These include the 7 mm Remington Magnum (7.2x64mm), .300 Winchester Magnum (7.8/7.62x67mm), and the .338 Lapua Magnum (8.6x70mm). These cartridges offer better ballistic performance and greater effective range than the 7.62x51mm. Though they are not as powerful as .50 calibre cartridges they are not as heavy as rifles chambered for .50 calibre ammunition, and are significantly more powerful than rifles chambered for 7.62x51mm.

Snipers may also employ anti-materiel rifles in sniping roles against targets such as vehicles, equipment and structures, or for the long-range destruction of explosive devices; these rifles may also be used against personnel.

Anti-materiel rifles tend to be semi-automatic and of a larger calibre than anti-personnel rifles, using cartridges such as the .50 BMG, 12.7x108mm Russian or even 14.5x114mm Russian and 20mm. These large cartridges are required to be able to fire projectiles containing payloads such as explosives, armour piercing cores, incendiaries or combinations of these, such as the Raufoss Mk211 projectile. Due to the considerable size and weight of anti-materiel rifles, 2- or 3-man sniper teams become necessary.

Barrel

Barrels are normally of precise manufacture and of a heavier cross section than more traditional barrels in order to reduce the change in impact points between a first shot from a cold barrel and a follow-up shot from a warm barrel. Unlike many battle and assault rifles, the bores are usually not chromed to avoid inaccuracy due to an uneven treatment.

When installed, barrels are often free-floated, i.e., installed so the barrel only contacts the rest of the rifle at the receiver, to minimise the effects on impact point of pressure on the fore-end by slings, bipods, or the sniper's hands. The end of the barrel is usually crowned or machined to form a rebated area around the muzzle proper to avoid asymmetry or damage, and consequent inaccuracy. Alternatively, some rifles such as the Dragunov or Walther WA2000 provide structures at the fore-end to provide tension on the barrel in order to counteract barrel drop and other alterations in barrel shape.

External longitudinal fluting that contributes to heat dissipation by increasing surface area while simultaneously decreasing the weight of the barrel is sometimes used on sniper rifle barrels.

Sniper rifle barrels may also utilise a threaded muzzle or combination device (muzzle brake or flash suppressor and attachment mount) to allow the fitting of a sound suppressor. These suppressors often have means of adjusting the point of impact while fitted.

Military sniper rifles tend to have barrel lengths of 600 mm (24 inches) or longer, to allow the cartridge propellant to fully burn, reducing revealing muzzle flash and increasing bullet velocity. Police sniper rifles may use shorter barrels to improve handling characteristics. The shorter barrels' velocity loss is unimportant at closer ranges; projectile energy is more than sufficient.

Stock

The most common special feature of a sniper rifle stock is the adjustable cheek piece, where the shooter's cheek meets the rear of the stock. For most rifles equipped with a telescopic sight, this area is raised slightly, because the telescope is positioned higher than iron sights. A cheek piece is simply a section of the stock that can be adjusted up or down to suit the individual shooter. To further aid this individual fitting, the stock can sometimes also be adjusted for length, often by varying the number of inserts at the rear of the stock where it meets the shooter's shoulder. Sniper stocks are typically designed to avoid making contact with the barrel of the weapon.

Accessories

An adjustable sling is often fitted on the rifle, used by the sniper to achieve better stability when standing, kneeling, or sitting. The sniper uses the sling to "lock-in" by wrapping their non-firing arm into the sling forcing their arm to be still. Non-static weapon mounts such as bipods, monopods and shooting sticks are also regularly used to aid and improve stability and reduce operator fatigue.

Variants

The M249 version of the Minimi was adopted by the US military in 1982; since 1984, production for the US military is carried out entirely in the US by a local subsidiary, FN Manufacturing LLC in South Carolina.

PIP-upgraded M249 SAW
A U.S. Marine fires the PIP-upgraded M249 SAW.

As part of the US military's M249 Product Improvement Program (PIP), the M249 was updated with: a new synthetic stock and modified buffer assembly, a single-position gas regulator, a “birdcage” type flash hider/compensator from the M16A2, a polymer barrel heat guard, and a folding carry handle. As a result, the weapon’s weight increased to 7.47 kg (16.5 lb). Many of the PIP upgrades were later incorporated by FN for the Minimi.

A lightweight variant of the Para with a Picatinny top cover rail adapter is known as the Minimi Special Purpose Weapon (SPW). It had the magazine feed port removed to further reduce weight, and a railed MIL-STD-1913 handguard was used that enables the use of standard tactical accessories.

Another variant of the SPW requested by the US Special Operations Forces is the Mk 46 Mod 0 that incorporates a lightweight fluted barrel but lacks the magazine feed system, vehicle mounting lugs and carry handle. A railed forearm ensures modularity and mission-adaptability permitting the use of flashlights, vertical grips, and infrared laser designators. An improved variant known as the Mk 46 Mod 1 with an improved forward rail and lightweight titanium bipod has been adopted by the United States Navy.

L108A1 version of the Minimi support weapon
A member of the Queen's Dragoon Guards fires the L108A1 version of the Minimi support weapon.

The Minimi prototype was originally designed in 7.62x51mm NATO, and later redesigned around the 5.56mm cartridge. When the USSOCOM issued the requirements for the Mk 48 Mod 0, the original plans for the Minimi were retrieved and used to develop this new model. As a result of favorable reviews of the Mk 48 Mod 0 and increasing demand for a more powerful variant of the Minimi, FN Herstal introduced the Minimi 7.62, available in several different configurations. Apart from the different caliber, the Minimi 7.62 incorporates a non-adjustable, self-regulating gas system and a hydraulic recoil buffer in the buttstock assembly. The Minimi 7.62 also has a different sight setup calibrated for the larger cartridge. The rear sight is adjustable from 100 to 1,000 m by 100 m increments. The sight can also be corrected for windage. A variant of the Minimi 7.62 equipped with a railed Picatinny handguard is the Minimi 7.62 TR.

Copies of the Minimi have been produced in China, called the XY 5.56 x 45, produced in 5.56x45mm NATO. It is meant for export.

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