History of U.S. Military Machine Guns: Part 3
Vietnam War—Present Day
By the end of World War II, engineers largely had the concept of the machine gun figured out. Air-cooled designs now functioned well at high rates of fire, and strategies for effectively using suppressing fire had been developed and battle tested. As with the progression of any technology, guns got smaller and lighter as time went on. At this point in machine gun history, nearly all the firearms used by the U.S. were largely just improved versions of earlier actions, usually those created by the late John Moses Browning.M60 General Purpose Machine Gun (1957)
After World War II, there was a push for a new, lighter machine gun that could be more easily used at the infantry level, and still serve multiple roles as a fixed-position gun. To that end, development of the M60 machine gun started in the late 40s. The design capitalized on captured German technology from the FG 42 and MG 42, as well incorporating influences from the failed M1941 Johnson LMG.
The FG42 was basically an improved Lewis Gun, with the Germans building upon the effective design by the American inventor. American engineers would borrow from that, copying the overall layout, bolt, and gas piston system. The MG 42 struck fear into the hearts of American G.I.s with its exceptional rate of fire, earning the nickname Hitler’s Buzz Saw, because of its distinctive sound. The belt feed components and top cover were appropriated from this design for the M60.
Early prototypes, such as the T52 and T161, looked like a child born from marriage of the M1941 Johnson LMG and the FG 42. The sum of these parts was a gas-operated, air-cooled, belt-fed machine gun capable of full-auto fire only. Of particular note is the unique gas system, which used the “gas expansion and cutoff” principle also found in the M14.
This system was simpler than many of its contemporaries, and was particularly easy to clean. The resultant gun was known as the T161E3, which was changed to M60 when the U.S. Army officially adopted it in 1957. The new weapon fired 7.62x51mm NATO from an open-bolt at a rate of 550 rounds per minute.
The M60 would become the face of Vietnam conflict, finding its way into the bush and skies alike, with all branches of service. It served as the door gun in the infamous Huey helicopter that both put many in harms way as well as ushering them to safety.
The gun was nicknamed “The Pig,” by grunts in the field, though the origins of that nickname are a bit muddy. Some say the gun earned the moniker because of its 24-pound weight, while others contend that the sound it made resembled that of a hog.
One thing is certain, every member of a squad would carry 200 rounds of belted ammo to feed The Pig, with some carrying spare barrels as well.
The original M60 was designed to be a crew-served machine gun, with one man shooting, and another feeding the ammo belt. Later variants made the system much easier to operate by one person.
The gun used 7.62 NATO ammunition in a disintegrating belt held together by M13 links, which replaced the M1 links used with the M1917 and M1919 Browning machine guns in the mid 20th century.
Anyone that is an Alice in Chains fan likely knows the story about guitarist and lyricist Jerry Cantrell’s father, as told in the song Rooster. The gun the protagonist used was likely an M60D, a pintle-mounted variant of the M60 that saw service as the door gun in most of the choppers that visited sunny Southeast Asia during the Vietnam War.
It replaced the short-lived M60B, which was held by the gunner—obviously not a good solution. Unlike other models in the M60 line up, the D has spade grips. It also features a ring-type sight more typically found on aircraft guns.
To prevent helicopter engines from ingesting spent casings from the gun, which could cause a real problem, the M60D was fitted with a canvas brass catcher to intercept ejected casings and links before they caused an issue. The gun is most associated with the UH-1B Huey, but it also found its way onto the CH-47 Chinook, the ACH-47A, and on the UH-60 Black Hawk.
The M60D has been mostly replaced by the M240H on U.S. aircraft, but U.S. Ordnance-built M60Ds are still used on the SH-60 Seahawk.
Despite drawing on a number of successful firearms and serving through the Vietnam War and into the 1980s, the gun was not without its flaws. The fire control mechanism was known to fall out if jarred hard enough to defeat the single spring locking it in place. There were stories of M60 gunners reaching down to find their pistol grip and trigger missing, dropped somewhere a few miles back in the dense brush.
The gas system was held in place with a single nut, which could walk off with recoil and the heat of long strings of fire. This was remedied in the field by wiring the nut in place, which significantly slowed barrel changes.
The lack of a carrying handle also created issues when it came time to switching barrels. The Army issued an asbestos mitt to grab hot barrels, much like it did for the M1919 in WWII. But getting this glove on in the midst of a firefight was less than ideal.
Additionally, the way the action was designed required a metal part attached to the barrel to actually impact the bolt face during firing, sending it backward. This caused peening, which was remedied by regular filing to keep the guns running and often required replacement of the bolt after enough use.
The metal in the receivers was made relatively thin to save on weight. While many served well through Vietnam, later in life, when they’d had a few thousand rounds through them, they began to fail and spread apart. This was a particular problem in the 1980s when a lot of M60s were nearing the end of their lifespan.
The Army went back to the drawing board in an effort to rectify these issues. The first attempt was designated the M60E3. The first issue they sought to address was the gun’s weight, shaving ounces wherever they could to drop from 23 to about 18.5 pounds.
These reductions in weight also included making the barrel thinner, which required the cyclic rate to be turned down to 200 rpm.
Some claimed that the Stellite Superalloy barrel liner that was added made long strings possible, but the excessive heat generated usually shut down operation of the gun. To deal with this, two barrels were created, a lighter variant for infantry use and a heavier one more suited to prolonged suppressive fire from a fixed position.
A few features were added on the M60E3 to make the gun more useful in the field. It included a bipod attached to the forearm, which didn’t complicate barrel changes, and greatly improved stability. A vertical forward grip was also included, allowing the operator to fire from a standing position and from the shoulder. An ambidextrous safety was welcomed by gunners, as was the universal sling attachment points that meant the gun didn’t always have to be carried over one’s shoulder.
A carrying handle was added to the barrel, which facilitated swapping hot barrels without gloves. The gas system was simplified in an effort to speed cleaning. The reduced-weight parts found life on the battlefield difficult; as a result, durability suffered. The gun unfortunately now experienced more breakages and accelerated wear than its predecessors.
The next evolution is the M60E4, built to eliminate the problems that were created during the last round of tinkering. Externally, the gun stayed much the same, but was given a different forward grip, iron sights, butt stock and bipod. Most of the changes occurred on the internal components, with a goal of enhanced reliability.
The feeding system was given a facelift, fitted with a new pawl that pulled the belt with greater force. Early models had a duckbill flash suppressor, though these were ultimately phased out.
The gun gained a few pounds, but still remains lightweight at about 20.5 lbs. The footprint was also shrunk a bit to make it easier to maneuver in the tight spaces often encountered in jungle and urban warfare. As a result, the automatic weapon can be shoulder-fired with a fair degree of accuracy. The M60E4 now has multiple M1913 Picatinny rails for mounting optics, lasers, night vision systems and other accessories.
The gun can be used on all NATO Standard mounts, though some do require an adaptor. All of the major components interchange with the legacy M60s, with U.S. Ordnance manufacturing a conversion kit to upgrade older models. Despite these advances, the M60 was largely phased out in the U.S. military by the adoption of the M249 SAW.
The Colt Machine Guns (1965)
The Vietnam War-era wasn’t without its share of experimentation. Colt attempted to create a machine gun that it could market alongside the CAR-15, its take on the M16 family of weapons. Like the M16, the first Colt Machine Gun, or CMG-1, fired 5.56x45mm NATO cartridges, though it did so from an open bolt to shed heat.
The CMG-1 was belt-fed, but it did share a few parts with the CAR-15. One CMG-1 was built with a direct gas impingement design that shared a gas tube and bolt with the M16 family, but following models utilized pistons instead. Other shared features included pistol grip, front sight, and flash hider.
The CMG-1 was quickly replaced by the CMG-2, which ditched all of the M16 components, though it used an M16-like bolt with a unique double-sided firing pin that could be reversed if one side got broken.
In a belt-fed configuration, spent rounds ejected down the unused mag well. It lacked a charging handle, instead oddly using the pistol grip to chamber a round. The operator unlocked the grip and slid it forward and back to move a round from the belt into the chamber and cock the weapon.
A buttstock-less short-barreled CMG-2 saw trials with the Navy SEALs, but they never adopted it. Colt gave the project one more go with the CMG-3, a 7.62mm version, but hung it up for good by the mid-1970s.
Stoner 63 Machine Gun System (1963)
The World Wars had John Moses Browning and the Vietnam War had Eugene Stoner. Best known for the development of the Armalite AR-15/M16 rifles, AR-10, and AR-7 survival rifle, Stoner experimented with a modular weapons system in the early 1960s that also fired the 5.56x45mm NATO round, though early in the gun’s development it was chambered for 7.62x51mm (.308 Win).
The Stoner 63 was a modular system that used a variety of interchangeable components that allowed it to be transformed into a rifle, carbine, a top-fed light machine gun (called an Automatic Rifle in the system’s nomenclature), a belt-fed squad automatic weapon, or a vehicle mounted machine gun, all with the same receiver. The was largely made possible by the fact that the receiver was designed to be invertible.
The first working prototype of the forward thinking design was completed in 1962 and designated the Stoner M69W, as this reads the same upside down as it does right side up and Eugene felt this illustrated his vision of a fully invertible receiver.
Stoner saw that the military gun world was trending toward the 5.56, so the 7.62x51mm chambering was soon abandoned so the M63 could be more in line with the M16. The gun was redesignated as the Stoner 63, because production began in 1963.
Somewhat uniquely, the gas-operated weapons fired from a closed bolt to ensure maximum accuracy when being utilized as a rifle, but fired from an open bolt when used as machine gun to shed heat. The buffering system is also unique. A series of conical-spring washers absorb energy from the bolt by deforming into a flat plate. When the washers return to their original shape, they propel the bolt forward only slightly slower than the original recoil velocity. This cushioning effect was designed to extend the weapon’s service life.
The 63 saw service early in its development with a detachment of Navy SEALs sent to Southeast Asia. Members of the Marine Corp were issued the Stoner invention in 1967 for evaluation. The 63 was sent in rifle and carbine configurations, with limited numbers distributed as an Automatic Rifle to fill the role of squad automatic weapon. The Army was next to test the gun, sending it to select Army Special Forces units for evaluation in 1970.
The Army rejected it due to its relatively complex design and high maintenance requirements. The SEALs continued to use the Stoner 63, until the late 1980s when it was phased out in favor of the M249 SAW. Most of the remaining guns were destroyed.
One of the reasons the gun found success with spec ops units like the SEALs and not with the USMC or the Army all has to do with maintenance.
The Stoner 63 was a relatively complex firearm, and it was durable enough to be used on a mission, brought back to base, and carefully cleaned and serviced before the next mission, it worked great. But when it came to extended deployments in the jungle, where the firearm would see daily mud, rain, and regular use over the course of weeks in the field, the 63 wasn’t robust enough and had too many parts that could be lost.
M240 General Purpose Machine Gun (1977)
Built by Belgian firm FN Herstal and imported by FN America, the Mitrailleuse A Gaz, or MAG for short, was designated the M240 when it was adopted by U.S. forces.
The M240 is a 7.62x51mm NATO gas-operated, air-cooled, belt-fed general-purpose machine gun typically served by a crew. The gun can be employed in a number of ways as it can be fired effectively from its integral bipod, mounted on a tripod, or mounted on land, air, or sea vehicles. One of the gun’s biggest advantages is its standardization amongst NATO countries, which means parts are available from allies.
Like many machine guns capable of high rates of fire, the M240 uses an an open bolt system. To control the cyclic rate, the gas regulator may be configured in one of five settings. This is not a simple operation, however, as the barrel must be dismounted and the gas collar removed before the regulator can be adjusted. This is usually only performed in the field as a stopgap measure when excess fouling has affected the rate of fire adversely and cleaning the weapon can’t be performed. Rate of fire settings include 650–750, 750–850, or 850–950 rounds per minute.
The M240 was initially procured as a replacement for aging tank-mounted guns that were plagued with reliability issues. The FN Mag went up against the M60 in a series of tests. The two guns were evaluated for mean rounds between stoppages, which are malfunctions that can be cleared quickly, and mean rounds between failures, which are malfunctions that render the gun inoperable, such as a part breaking.
In 50,000 rounds fired, the FN gun scored remarkably higher, with 2,962 mean rounds between stoppages compared to the M60’s 846. Mean rounds between failure numbers were equally shocking: 6,442 and 1,669 respectively.
In 1977 the FN MAG was officially adopted as the U.S. Army’s standard vehicle machine gun, with the Marine Corps also selecting it for use on some armored vehicles. As older M60 machine guns aged out of service, the M240 would replace them. The Navy SEALs continued to use a variant of the M60 because of its slower rate of fire, which helped conserve ammunition. As popularity of the M240 grew, it was pressed into service with infantry units.
In 1991, the M240 officially replaced the M60 in the Marine Corps’ infantry. The Army followed suite shortly thereafter. The M240 all but replaced the M60 in most applications and roles, with Navy being the only holdout.
Rumors abound regarding the fate of the M240 as well as the M2, as designers with U.S. Special Operations Command and Marine Corps are working on a replacement, which they’ve dubbed the Lightweight Medium Machine Gun. The new automatic weapon will fire .338 Norma cartridges, and is slated for service within three years.
M249 Light Machine Gun (LMG) – Squad Automatic Weapon (SAW) (1984)
The M249 is another FN Herstal gun, known in Belgium as the Minimi. Both guns are gas-operated and air cooled, but a .308 Win version of the Belgian version was also produced, dubbed the Maximi. The M249 was only ever chambered in 5.56.
Army brass was looking for a new Squad Automatic Weapon in the 1980s, and felt the FN design would fit the bill, though it would be produced in South Carolina by FN Manufacturing LLC, not Belgium. The M249 has the advantage of being belt-fed or firing from STANAG-pattern magazines, so operators could utilize M4 and M16 mags if needed. The relatively lightweight SAW provides excellent accuracy for a gun with such a high rate of fire.
In an effort to provide troops with a lightweight weapon capable of sustained automatic fire, the Army Small Arms Program sought out a light machine gun in 5.56x45mm beginning in 1968. Popular thinking in the military at the time is that the 5.56 rounds were underpowered, so no money was allotted for the project.
New studies on the effectiveness of 5.56 and experiences with the Stoner 63, turned the tide on that way of thinking. The Army approved development of a new LMG, giving birth to the term Squad Automatic Weapon (SAW) in July of 1970, though no caliber was specified at the time.
A series of trials took place involving a number of different firearms from various manufacturers in various calibers, including 5.56 and 6mm, in the period between 1974 and 1980.
When the dust settled in May of 1980, the FN entry was selected based on performance and cost. The gun was tweaked, and testing of the new version started in June of 1981. It would be officially accepted into service in with the Army as the M249 SAW in 1984, with the USMC following a year later. Use in the field showed that there were some rough edges with the new design—literally.
Users complained about the lack of adequate heat shielding on the barrel and sharp edges that tended to injure operators. The front sight also required proprietary tools for adjustment, which was less than ideal. Production was suspended in 1985, and all M249s that weren’t already in service were to remain in storage until such time that a product improvement program could be implemented.
Due to budget issues, this process took a couple of years, but the bugs were eventually worked out and the barrel, hand guard, stock, pistol grip, buffer, and sights were modified.
The M249 remains in service to this day, filling the void left when the Army retired the BAR. Store of existing M249s are being carefully refurbished as needed, but there is talk of replacing the gun. The Army started soliciting bids for the Next Generation Squad Automatic Rifle (NGSAR) to replace the M249 in early 2017. They are looking for an even lighter weapon, with a stated weight requirement of 12 pounds, including sling, bipod, and suppressor.
They are also looking for improved long-distance engagement, with a targeted range of 600 meters for precision shooting or 1,200 meters for suppressing fire. The Marine Corps has already tested the M27 Infantry Automatic Rifle, with plans to supplement and partially replace the M249 with the lighter magazine-fed rifle. The Corps plans to buy as many as 4,100 IARs. Only time will tell how much longer the M249 will be in service and what its replacement will be.