Post by WYATT666 on Jan 14, 2009 11:28:38 GMT
The Minimi (short for French: Mini Mitrailleuse; “mini machine gun”) is a Belgian 5.56 mm 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, among them: Australia, Belgium, Canada, France, Greece, Italy, Indonesia, Malaysia, New Zealand, Thailand, Sweden, the United Kingdom and the United States (as the M249 SAW). The weapon is currently manufactured at the FN facility in Herstal as well as being license-built in Australia, Greece and the USA (by FN Manufacturing LLC). The Minimi is configured in several variants, the standard model (as a platoon or squad support weapon), the Para version (for use with armored vehicle crews, helicopter pilots and parachute infantry) and the vehicle model (as secondary armament for fighting vehicles).
Design details
The Minimi is an air-cooled automatic weapon, capable of fully automatic fire only, that uses a gas piston operating system with a short-stroke piston. The barrel is locked with a rotary bolt, equipped with two massive locking lugs, forced into battery by camming guides 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 eliminates 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 slowing heating. Gas escaping the gas cylinder is directed upward, avoiding kicking up dust and debris that would reveal the shooter's position. 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/min to 950-1150 rounds/min 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 forward, bottom right side of the receiver, protected with a dust cover. The Minimi is striker-fired and the bolt carrier functions as the striking mechanism.
The weapon is fed from the left-hand side by disintegrating-link M27 ammunition belts (a miniaturized version of the 7.62 mm M13 belt), from either an unsupported loose belt, enclosed in an ammunition box with a 200-round capacity (made of a synthetic polymer) attached to the base of the receiver, or from detachable STANAG magazines, used in other NATO 5.56 mm assault rifles such as the M16 and FNC. Magazine feeding is used only as an auxiliary measure, when belt-linked 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 under 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 innovative feature was developed by FN's Maurice V. Bourlet (US patent 4112817) and allows the Minimi to pass instantaneously 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 MG42. 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.
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, currently a modified grip with lateral grooves is used, installed at a smaller angle to the receiver.
The barrels used in the Minimi have an increased heat capacity for sustained fire, feature a chrome-lined rifled bore (6 right-hand grooves) and are manufactured in two versions: with a 178 mm (1:7 in) twist rate used to stabilize the heavier Belgian 5.56x45mm 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 will be able to perform a barrel change and ready the weapon for aimed fire in only 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.
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.
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.
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. Standard equipment supplied with the Minimi consists of three ammunition boxes with a 200-round capacity each, a cleaning kit stored inside the forearm, lubricant bottle, sling and blank-firing adaptor.
Variants
The M249 version of the Minimi was adopted by the US military in 1982, and since 1984, production is carried out entirely in the US by a local subsidiary - FN Manufacturing LLC in South Carolina.
As part of the US military's M249 PIP (Product Improvement Program), 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 SPW (Special Purpose Weapon). 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.
The Minimi prototype was originally designed in 7.62x51mm NATO, and later redesigned around the 5.56 mm 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.
Design details
The Minimi is an air-cooled automatic weapon, capable of fully automatic fire only, that uses a gas piston operating system with a short-stroke piston. The barrel is locked with a rotary bolt, equipped with two massive locking lugs, forced into battery by camming guides 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 eliminates 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 slowing heating. Gas escaping the gas cylinder is directed upward, avoiding kicking up dust and debris that would reveal the shooter's position. 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/min to 950-1150 rounds/min 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 forward, bottom right side of the receiver, protected with a dust cover. The Minimi is striker-fired and the bolt carrier functions as the striking mechanism.
The weapon is fed from the left-hand side by disintegrating-link M27 ammunition belts (a miniaturized version of the 7.62 mm M13 belt), from either an unsupported loose belt, enclosed in an ammunition box with a 200-round capacity (made of a synthetic polymer) attached to the base of the receiver, or from detachable STANAG magazines, used in other NATO 5.56 mm assault rifles such as the M16 and FNC. Magazine feeding is used only as an auxiliary measure, when belt-linked 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 under 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 innovative feature was developed by FN's Maurice V. Bourlet (US patent 4112817) and allows the Minimi to pass instantaneously 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 MG42. 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.
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, currently a modified grip with lateral grooves is used, installed at a smaller angle to the receiver.
The barrels used in the Minimi have an increased heat capacity for sustained fire, feature a chrome-lined rifled bore (6 right-hand grooves) and are manufactured in two versions: with a 178 mm (1:7 in) twist rate used to stabilize the heavier Belgian 5.56x45mm 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 will be able to perform a barrel change and ready the weapon for aimed fire in only 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.
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.
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.
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. Standard equipment supplied with the Minimi consists of three ammunition boxes with a 200-round capacity each, a cleaning kit stored inside the forearm, lubricant bottle, sling and blank-firing adaptor.
Variants
The M249 version of the Minimi was adopted by the US military in 1982, and since 1984, production is carried out entirely in the US by a local subsidiary - FN Manufacturing LLC in South Carolina.
As part of the US military's M249 PIP (Product Improvement Program), 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 SPW (Special Purpose Weapon). 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.
The Minimi prototype was originally designed in 7.62x51mm NATO, and later redesigned around the 5.56 mm 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.