FN 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 . 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 . 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 . 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 . 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 : 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 . 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 26 . 3 lb empty . M240L . The M240L ( or M240B Weight Reduction Program , formerly the M240E6 ) , is intended to reduce the weight 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 . 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 . 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 . The M240B is a successful and well - regarded 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 : 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 : 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 ) . Weight : Length : Barrel length : Width : Height : Cartridge : Action : Rate of fire : Muzzle velocity : Effective range : Maximum range : Feed system : Sights :