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An M240.

The M240, 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 in use with the United States Armed Forces since the mid-1980s. It is used extensively by infantry, 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 NATO ammunition. The M240s used by the US military are currently manufactured by FN Manufacturing, a US-based branch of FN Herstal.

Development[edit | edit source]

Manufactured by Fabrique Nationale, the FN MAG was chosen by the U.S. military for different roles after large world-wide searches and competitions. It has mainly replaced the M60 in most roles, though it replaced some other machine guns in the coaxial position. M60s have remained in use, but they are being slowly phased out and replaced by the newer M240s as they wear out.

The MAG is a belt-fed, gas-operated, air-cooled, crew-served, fixed headspace weapon. Its functionality is demonstrated by its ability to be mounted on the M122A1 tripod, a bipod, on vehicles, or on aircraft. The M60 is still, in some cases, used as a door gun on Army helicopters, however.

An M240L on a tripod.

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 for the Army and Marine infantry. While possessing 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 greater manufacturing cost and weight.

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 it is quite reliable for its mass.

Testing and adoption[edit | edit source]

The adoption of the MAG has its origins in the late 1960s/early 1970s as a project to procure a new coaxially mounted 7.62 mm 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. It was deployed in these new roles in the 1990s and 2000s.

An M240D in an SH-60.

As mentioned, during the 1970s the Army was looking for new 7.62 mm 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 a 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 1,750 5,500

The test applies only to the 70s-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 would be adapted by the infantry later on, spawning the M240B and M240G. It 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 M240 would be 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.

Variants[edit | edit source]

The manufacturer's name for the 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[edit | edit source]

This was adopted in 1977 by the Army to replace the M73 and M219 7.62 mm 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[edit | edit source]

The M240B is the standard infantry medium machine gun of the U.S. Army and recently, the U.S. Marine Corps. 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 is also mounted aboard ships and small boats. It is almost always referred to as an "M240 Bravo" or even just "240" verbally, but always written as M240B.

A sailor firing an 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 1000 existing M240s being sent to FN for an overhaul and a special kit that modified them for use on ground (such as a stock, a rail, etc.). This led to procurement contracts in the late 1990s for all-new M240B. 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, and there is a program underway for a new lightweight medium machine gun in the early 2000s. The Army M240 converted to the M240B configuration should not be confused with the large numbers of M240/E1 converted to the M240G configuration for the Marine Corps.

M240C[edit | edit source]

The M240C is a variation on the original coaxial (installed alongside the main weapon) M240, but with a right-handed feed for use on the M2/M3 Bradley Fighting Vehicle and LAV as the coaxial machine gun.

M240E1 and M240D[edit | edit source]

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 accommodates 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 fire power. 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[edit | edit source]

An M240G on a tripod.

The M240 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, 7.62 mm 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 25.6 lb. The M240G has three gas settings, allowing this weapon to fire between 650 and 950 rounds per minute.

M240E5/M240H[edit | edit source]

An improvement of the M240D, the M240H features a

An M240H in a CH-47.

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 26.3 lb empty.

M240L[edit | edit source]

The M240L (or M240B Weight Reduction Program, formerly the M240E6), is intended to reduce the weight

An M240L.

of the existing M240B by five pounds. The resulting improvements will reduce the Soldier’s combat load while allowing easier handling and movement of the weapon. It is expected to be type classified in the fourth quarter of fiscal year 2010.

Operation[edit | edit source]

Loading the weapon is performed by pulling the charging handle which locks the bolt to the rear. The weapon is placed on safe and the charging handle is pushed forward (this is spring loaded on the tank mounted version). The feed tray cover is then lifted and rounds are laid inside the feed tray. The feed tray cover is then closed and the weapon is ready for operation.

The weapon fires from the open bolt position meaning the bolt is held to the rear and only moves forward as it 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 an open bolt also provides the possibility 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.

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 another rigid object. If there is a live round lodged in the barrel, the operator must immediately decide if the barrel is hot enough that there is a chance of it cooking off. If there is, he will immediately move his face away from the opening of the weapon. 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 of 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 in ensuring that the weapon is pointed in a safe direction first.

A Marine fires an M240G.

The rate of fire may be controlled by three different settings. The first setting allows the weapon to cycle at 750 round/min. The two remaining settings increase the rate of fire by 100 round/min per setting (the second setting being 850 round/min, and the third setting 950 round/min). 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.

The barrels can be exchanged rapidly, thanks to a barrel release button located on the left side of the weapon. The weapon is cleared first and then the button is held down, while the barrel's carrying handle is moved from the right side of the weapon to the center, unlocking it from the receiver. At this point, the button is released and the barrel is then pulled free of the receiver and placed to the side. The new barrel is inserted into the receiver and then the carrying handle is shifted to the right, locking it into place.

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

Feedback on the M240B[edit | edit source]

The M240B is a successful and well-r

An HMMWV mounted M240B.

egarded weapon system that has proven itself in combat in Afghanistan and Iraq, serving as a powerful supplement to the lighter 5.56 mm-based M249, M16 and M4. Its 7.62 mm round provides good penetration and stopping power, a characteristic that is especially appreciated in the urban environments where many Iraqi engagements take place. Overall, the M240B's combat record must be considered superior to the problematic M60 that it has for the most part replaced in US service. 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 (barrels, springs, small roll pins, T&E pin, heat shields, sear pins, spare barrel bag, cleaning materials);
  • One soldier reported a double feed in combat;
  • 50% reported that they need better ways to carry ammunition (ammo bag, etc.);
  • 100% were confident in their weapon;
  • 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.

On 15 May 2003, An "Operation Iraqi Freedom PEO Soldier Lessons Learned" report by LTC Jim Smith, U.S. Army, was published. The report made the following comments on the M240B:

Soldiers have great confidence in this weapon. Again, the vast majority of comments were positive. Most negative comments were relative to the AG’s load. Soldiers recommended fabricating the tripod out of a lighter material. The AG bag is not integrated into the remainder of the MOLLE and, therefore, is not easily carried. Additionally, the nylon bag melts when it comes in contact with a hot barrel. Other suggestions included adding collapsible bipod legs like the squad automatic weapon (SAW), wiring down the heat shields and an ammunition carrying system to carry 300-400 linked rounds.

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

  • Soldier ratings 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 (Active, Guard and Reserve).

Specifications(M240B)[edit | edit source]


  • 25.99 lb (11.79 kg)


  • 49.7 in (1,263 mm)

Barrel length:

  • 24.8 in (630 mm)


  • 4.7 in (118.7 mm)


  • 10.4 in (263 mm)


  • 7.62×51mm NATO


  • Gas-operated, open bolt

Rate of fire:

  • 650–1,000 rounds/min

Muzzle velocity:

  • 2,800 ft/s (853 m/s)

Effective range:

  • Bipod: 880 yd (800 m)
  • Tripod: 1,800 m (1,980 yd)

Maximum range:

  • 4,074 yd (3,725 m)

Feed system:

  • Non-disintegrating DM1 or disintegrating M13 linked belt


  • Folding leaf sight with aperture and notch, front blade

See also[edit | edit source]

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