M240 machine gun

M240B

The M240, officially Machine Gun, 7.62mm, M240, is the US military designation for the FN MAG, a family of belt-fed, gas-operated medium machine guns firing the 7.62x51mm NATO cartridge.

The M240 has been used by the United States Armed Forces since the mid-1980s. It is used extensively by infantry, most often rifle companies, as well as ground vehicles, watercraft, and aircraft. Despite not being the lightest medium machine gun in service, it is highly regarded for reliability, and its standardization among NATO members is also seen as a major advantage.

All variants are fed from disintegrating belts, and are capable of firing most types of 7.62 mm (.308) NATO ammunition. There are significant differences in weight and some features among some versions which restrict interchangability of parts. The M240s used by the US military are currently manufactured by FN manufacturing, a US-based branch of FN Herstal.

Development

M240 coaxial machine gun aboard an M1 Abrams tank.

Manufactured by Fabrique Nationale, the FN MAG was chosen by the U.S. military for different roles after large world-wide searches and competitions. The MAG is a belt-fed, gas-operated, air-cooled, crew served, fixed-headspace weapon. Its versatility is demonstrated by its ability to be mounted on the M122A1 tripod, a bipod, on vehicles, or on aircraft.

It was first adopted by the U.S. Army in 1977, as a coaxial tank gun, and slowly adopted for more applications in the 1980s and 1990s. The M240 and M240E1 were adopted for use on vehicles. This led to further adoption in more uses, especially in the Army and Marine Corps. While posessing many of the same basic characteristics as its predecessor, the durability of the MAG system results in superior reliability when compared to the M60. The MAG actually has a more complex gas system than the M60, but gives better reliability combined with lower maintenance requirements, though this comes at a greater manufacturing cost.

Compared to other machine guns, its rating of 26,000 Mean Rounds Between Failure (MRBF) is quite high for its weight-in the 1970s when it was first adopted it achieved about 7,000 MRBF. It is not as reliable as some very heavy older designs, but is still quite reliable for its mass.

Early history: testing and adoption

Members of an M1 Abrams main battle tank vrew man the tank commander's M2 .50 caliber machine gun, left, and the ammunition loader's M240 (a second M240 is mounted coaxially to the M68A1 105mm main gun, but is not visible).

The US adoption of the MAG has its origins in the late 1960s/early 1970s as a project to procure a new coaxially mounted 7.62mm machine gun for tanks to replace the M73 and M219 machine guns then being used. It would go on to be deployed in this role in the 1980s, but was additionally adopted for infantry and other uses.

As mentioned, during the 1970s the Army was looking for new 7.62mm machine guns for vehicle/AFV mounts. The 1950s-era M73 had been rather troubled, and the derivative M73E1/M219 was not much of an improvement. A number of designs of the period from various countries were considered; the final two candidates were the M60E2 and the FN MAG. They underwent comprehensive testing alongside the older M219 for comparison.

Two main criteria analyzed were Mean Rounds Between Stoppages (MRBS, jams that can be cleared within minutes) and Mean Rounds Between Failures (MRBF, such as part breaking). The results for the evaluated machine guns were the following:

Type	Rounds fired	MRBS	MRBF
FN MAG 58	50,000	2,962	6,442
M60E2	50,000	846	1,669
M219	19,000	215	1,090
Minimum specified		850	2,675
Minimum desired		1,650	5,500

The test applies only to the 1970s-era versions tested. The MAG itself underwent some improvements and the M60E2 was a specialized coaxial variant that differed from some of the other types. The qualities of the M60 variants vary considerably, such as between the M60E4 and the M60C. That aside, for these types the clear winner was the MAG, which was designated as the M240 in 1977 after the Army competition. It went on to replace many older types for the vehicle/coaxial role in the 1980s. The M240 proved popular enough that it was adapted by the infantry later on, spawning the M240B and M240G. The M240G was adopted for this role in 1991 by the USMC, replacing the rather worn M60s used by infantry, but also the M60E3 that the Marines had started using in the 1980s. The M240B was adopted in the late 1990s by the Army for infantry, beating out the M60E4, which though lighter and cheaper did not offer commonality with the vehicle borne M240, other NATO FN MAG users such as Britain, or the USMC.

The various versions of the M240 have not yet entirely replaced all the M60 versions, though they have for most main applications and roles. The M60 is still, in some cases, used by the Navy.

Variants

A Marine inserts an ammunition belt into the feed tray of the M240G.

The manufacturer's name for this weapon is the MAG 58. The M240 adheres to FN MAG 58 specifications, allowing parts to be interchanged with other standard MAG 58s. This has significant advantages in training, logistics support, tactical versatility, and joint operations. For example, a US unit with attached British troops could supply replacement parts for the L7s, and vice versa.

M240

This was adopted in 1977 by the Army to replace the M73 and M219 7.62mm machine guns, and the M85 .50 cal. In the 1980s, the Marines adopted the M240 and M240E1 for use on vehicles like the LAV-25.

M240E4/M240B

A Seabee fires an M240B mounted atop a Humvee.

The M240B is the standard infantry medium machine gun of the U.S. Army. It is also in service with the U.S. Air Force, Navy, and Coast Guard. It comes configured for ground combat with a buttstock and bipod, though it can also be mounted aboard shipts and small boats. It is almost always referred to as an "M240 Bravo" or even just "240" verbally, but always written as M240B. the M60E4 (Mk 43 as designated by the U.S. Navy) was pitted against the (then called) M240E4 in Army trials during the 1990s for a new infantry medium machine gun, in a competition to replace the decades old M60s. The M240E4 won, and was then classified as the M240B. This led to 1,000 procurement contracts in the late 1990s for all-new

A Marine performs maintenance on an M240 pintle mounted machine gun, mounted on an LAV.

M240Bs. However, a new feature was added, a hydraulic buffer system to reduce the felt recoil as incorporated in the M60. While the M240B had been more reliable in the tests, it was a few pounds heavier than the M60E4, which led to the development of the ligher M240L machine gun. The Army M240 converted to the M240B configuration should not be confused with the large numbers of M240/E1 converted for the Marine Corps.

In the Marine Corps, the M240G is the predecessor to the M240B. The main differences between the two machine-guns variants is the picatinny rail system, hydraulic buffer inside the buttstock to reduce the amount of recoil felt by the gunner, and only one gas setting on the gas regulator plug. Where as the M240G had three different gas settings allowing for the machine gun to fire between 650-950 rounds per minute depending on the gas setting selected; the M240B only allows for one rate of fire of 650-750 rounds per minute. The reason the gas setting has been limited on the M240B is to slow down the rate of fire and allow for the longevity of the machine gun.

The M240B is being tested with a new adjustable stock that may replace the current stock of the M240B. The lighter M240L may replace the M240B in U.S. Army service.

M240C

M240B in use by a U.S. Army soldier.

The M240C is a variation on the original coaxial (installed alongside the main weapon) M240, but with a right-hand feed for use on the M2/M3 Bradley Fighting Vehicle and LAV as the coaxial machine gun. It is fed from the left on the M1 Abrams and other M1 variant tanks. The 240C uses a charging cable instead of a charging handle, has a cut-off pistol grip and has a special paddle assembly that allows the trigger to be acuated by means of a solenoid. Since the machine gun is not meant to be handled during use, the barrel is fully exposed and must be handled with asbestos mittens during barrel changes.

M240E1 and M240D

The M240E1 variant on a LAV-25.

The M240D has two possible configurations: aircraft and egress (ground). The aircraft configured M240D has a front and rear sight and a trigger group which accomodates the spade grip device. The ground configuration involves the installation of an Egress Package or "infantry modification kit" which is designed to provide downed aircrew personnel with increased firepower. The M240D is an upgrade of the M240E1, primarily in the addition of an optical rail on the receiver cover. The M240E1 is also fitted with spade grips for flexible use.

M240G

Marines with a tripod mounted M240G.

The M240G allows for commonality throughout the Marine Corps whether the weapon is used in an infantry, vehicular, or airborne role. The M240G is the ground version of the original M240 or M240E1, 7.62mm medium class weapon designed as a coaxial/pintle mounted machine gun for tanks and LAVs. The M240G can be modified for ground use by the installation of an "infantry modification kit", (a flash suppressor, front sight, carrying handle for the barrel, a buttstock, infantry length pistol grip, bipod, and rear sight assembly). The M240G lacks a front heat guard, and as such is a few pounds lighter than the M240B, weighing in at 25.6lb.

M240E5/M240H

an improvement of the M240D, the M240H features a rail equipped feed cover, an improved flash suppressor, and has been configured so that it can be more quickly converted to infantry standard using an Egress kit. The M240H is 41.2 in long with a 23.6 in barrel, and weighs 23.6 lb empty.

M240L

The M240L reduces the weight of the existing M240B by 5.5 lbs. To achieve 18% weight savings the M240L incorporates titanium construction and alternative manufacturing methods for fabricating major components. The resulting improvements reduced the soldier's combat load while allowing easier handling and movement of the weapon. The M240L may replace the M240B in U.S. Army service. It was type classified in the fourth quarter fiscal year 2010.

M240L 7.62mm Medium Machine Gun (Light) specifications:

• Operation: Gas-operated (full-auto)
• Length: 48.5 in
• Weight: 22.3 lb
• Caliber: ( 7.62mm NATO (7.62x51mm NATO))
• Maximum effective range: 1,800 meters
• Maximum range: 3,725 meters
• Tracer burnout: 900 meters
• Cyclic rate of fire (hydraulic buffer) 550-650 RPM

​Operation

Loading the M240 can either be done with the bolt forward or to the rear.

The weapon fires from the open bolt position, meaning the bolt is held to the rear and only moves forward as is firing a round. The firing pin is static and the bolt moves around the firing pin, circumventing any need for a hammer. A sear is used to time the internal mechanisms of the weapon to provide a consistent rate of fire ensuring proper function and accuracy. However, firing from the open bolt also provides the posibility of accidental discharge due to a bolt override. This happens when there is enough force for the bolt to jump over the sear and fire without the trigger being pulled. The safety on the weapon cannot stop this from happening. The safest way to protect against this is to leave the bolt forward on the weapon until the operator is ready to fire the weapon; then charge the weapon and fire.

Clearing the weapon is performed by ensuring the bolt is locked to the rear and the weapon is on safe. The feed tray cover is then lifted, the remaining belt (if any) is swept out of the feed tray, the feed tray is lifted to visually inspect the rear of the barrel and the face of the bolt. Any links or brass casings are removed. The weapon is now clear. In the unlikely event that a live round is on the bolt face, it is knocked loose with a cleaning rod or other rigind object. If there is a live round lodged in the barrel, the operator must immediately decide if the barrel is hot enough tgat there is a chance of it cooking off. If there is, he will immediately move his face away from the opening of the weapon; and aiming the gun in a direction percieved to take the least amount of damage and/or casualties should the event of a cook-off occur. He should then wait for the barrel to cool off before attempting to remove it. In many cases, attempting to remove the barrel will cause the round to detonate as soon as the barrel is unlocked from the receiver. He can also attempt to extract the round by taking the weapon off safe, pulling the trigger and pulling back on the charging handle. This has a fair chance of causing the weapon to fire, so care should be made to ensure that the weapon is pointed in a safe direction first.

The rate of fire may be controlle by three different settings. The first setting allows the weapon to cycle at 750 rpm. The two remaining settings increase the rate of fire by 100 rpm. These settings are changed by dismounting the barrel, removing the gas regulator collar and turning the gas regulator to allow more or less gas to move through the weapon system. It is generally performed before missions, as changing the setting is distracting at best under field or combat conditions.

During prolonged firing, care must be taken to not allow exposed skin to come in contact with the weapon. The barrel can become hot enough to inflict second degree burns instantly without becoming visibly different. These hot barrels glow brightly to anyone using any sort of optics sensitive to infared radiation, such as night vision devices.

Feedback on the M240B

The M240B is a successful and well-regarded weapon system that has proven itself in combat, serving as a powerful supplement ot the lighter 5.56mm based M249, M16, and M4. Its 7.62mm round provides good penetration and stopping power, a characteristic that is especially appreciated in the urban environments where many Iraqi engagements took place. Overall, the M240B's combat record must be considered superior the the problematic M60 machine gun that it has for the most part replaced. An April 2002 presentation by the Natick Soldier Center reported on lessons learned from M240B use in Afghanistan:

• 17% reported engaging the enemy with their M240B;
• 42% reported problems getting spare parts in Afghanistan;
• 1 soldier reported a double feed in combat;
• 50% reported that they need better ways to carry ammunition (ammo bag etc.);
• 82% felt that their M240B was reliable;
• 60% felt it needed to be easier to carry, and to set up;
• Suggestions, improved sling, lighter, more durable tripod, more durable heat shield;
• 100% were confident in their weapon.

A May 2006 presentation by the US Army Infantry Center reported these conclusions on the M240B:

• Soldier rating consistently highly positive

• Great rate of fire and target effects

• Good durability​

These comments were based on a survey of 3,300 soldiers from eight divisions of the U.S. Army.