The M60, officially the United States Machine Gun, Caliber 7.62 mm, M60, is a family of American general-purpose machine guns firing 7.62x51mm NATO cartridges fron a disintegrating belt of M13 links. There are several types of live ammunition apporved for use in the M60, including ball, tracer, and armor-piercing rounds.
Introduced in 1957, it has served with every branch of the U.S. military and still serves with other armed forces. Its manufacture and continued upgrade for military and commercial purposes continues into the 21st century, even though it has been replaced or supplemented in most roles by other designs, noteably the M240 in U.S. service.
The M60 is a belt-fed machine gun that fires the 7.62mm NATO cartridge commonly used in larger rifles. It is generally used as a crew served weapon, and is operated by a team of two to three individuals. The team consists of the gunner, the assistant gunner (AG in military slang), and the ammunition bearer. The gun's weight and the ammount of ammunition it can consume when fired make it difficult for a single soldier to carry and operate. The gunner carries the weapon and, depending on his strength and stamina, anywhere from 200 to 1000 rounds of ammunition. The assistant carries a spare barrel and extra ammunition, and reloads and spots targets for the gunner. The ammunition bearer carries additional ammo and the tripod with associated traversing and elevation mechanism, if issued, and fetches more ammunition as needed during firing.
The M60 can be accurately fired at short distances from the shoulder thanks to its design. This was an initial requirement for the design and a hold-over concept from the M1918 Browning Automatic Rifle. It may also be fired from the integral bipod, M122 tripod, and some other mounts.
M60 ammunition comes in a cloth bandolier containing a cardboard box of 100 pre-linked rounds. The M60 changed fron M1 link to the different M13 link, a change from the older link system with which it was not compatible. The cloth bandolier is reinforced to allow it to be hung from the current version of the feed tray. Historically, units in Vietnam used B3A cans fron C-rations packs locked into the ammunition box attachment system to roll the ammunition belts over for a straighter and smoother feed to the loading port to enhance reliability of feed. The later models changed the ammunition box attachment point and made this adaptation unnecessary.
The M60 machine gun began development in the late 1940s as a program for a new, lighter 7.62mm machine gun. It was derived from German machine guns of WWII, but it contained American innovations as well. Early prototypes, noteably the T52 and T161 bore a close resemblance to both the M1941 Johnson machine gun and the FG42. The final evaluation version was designated the T161E3. It was intended to replace the BAR and M1919A6 Browning Machine Gun in the squad automatic weapon rile, and in the medium machine gun role. One of the weapons tested against in during its procurement process was the FM MAG.
The U.S. Army officially adopted the T160E3 as the M60 in 1957. It later served in the Vietnam War as a squad automatic weapon with many US units. Every soldier in the rifle squad would carry an additional 200 linked rounds of ammunition for the M60, a spare barrel, or both. The up-gunned M113 armored personnel carrier ACAV added to M60 gunners beside the main .50 caliber machine gun, and the Patrol Boat, River had one in addition to two .50 cal mounts.
During the Vietnam War, the M60 received the nickname "The Pig" due to its bulky size.
During the 1980s, the M60 was partially replaced by the M249 Squad Automatic Weapon within the infantry squad. The M60 was retained in the vehicle mounted role and the general-purpose role due to its greater power and range compared to the 5.56mm M249. In United States Marine Corps service, concerns about the M60's reliability, weight, and the high round counts of many M60s in service prompted the adoption of the M60E4 to replace most original M60s in infantry units.
Starting with Ranger battalions, the US Army began adopting and modifying M240 variants to replace their remaining M60s in the early 1990s. The M240 is several pounds heavier than the M60, and has a longer barrel and overall length, but is more reliable in use and testing. However, the M60 uses a simpler gas system that, when care is taken during reassembly, is easier to clean. This is obviated by the fact that the gas tube is wired shut with lockwire to prevent the weapon from disassembling itself due to vibration in hard use.
The M60 continues to be used in the 21st century by US Navy SEALs and as a door gun on US Army helicopters, and was the main 7.62mm machine gun by some US special operations forces to the late 1990s. As of 2005, it is used by the Coast Guard, Navy, and some reserve units, though it is being phased out in favor of the M240 7.62mm medium machine gun. its use as an Army helicopter door gun will soon taper off, as an improved M240 version has been adopted for this role.
The M60 is a gas-operated, air-cooled, belt-fed, automatic machine gun that fires from the open bolt position and is chambered for the 7.62 mm NATO cartridge. Ammunition is usually fed into the weapon from a 100 round bandolier containing a disintegrating, metallic split-link belt.
The design drew on many common concepts in firearms manufacture of the period, such as stamped sheet metal construction, belt feed, quick barrel replacement, a pistol grip and stock, and a semi bullpup design similar to the FG42. The M60's operating system of an operating rod turning a rotating bolt was inspired by the FG42, which was based on the much earlier Lewis Gun. The M60's gas operation is unique, and drew on technical advances of the period, particularly the White "gas expansion and cutoff" principle also exploited by the M14 Rifle. The M60's gas system was simpler than other gas systems and easier to clean.
The straight-line layout allowed the operating rod and buffer to run directly back into the buttstock and reduce the overall length of the weapon.
As with all such weapons, it can be fired from the shoulder, hip, or underarm position. However, to achieve the maximum effective range, it is recommended that a bipod-steadied position or a tripod-mounted position be used and fired in bursts of 3-5 rounds. The weapon is heavy and difficult to aim when fired without support, though the weight helps reduce the felt recoil. The large grip also allowed the weapon to be conveniently carried at the hip. The gun can be stripped using a live round as a tool. However, this is highly discouraged, as doing so can damage that round and increase the chance of a misfire.
The M60 is often used with its own integral bipod or with the M122 tripod. The M60 is considered effective up to 1,100 meters when fring at an area target and mounted on a tripod; up to 800 meters when firing at an area target using the integral bipod; up to 600 meters when firing at a point target, and up to 200 meters when firing at a moving point target. USMC doctrine holds that the M60 and other weapons in its class are capable of suppressive fire on area targets out to 1,500 meters if the gunner is sufficiently skilled.
Originally an experimental M91 tripod was developed for the M60, but an updated M2 tripod design was selected over it which became the M122. The M122 would be iteself replaced in the 2000s by a new mount, in time for the M60 to also be used with it.
The M60 family of weapons are capable of firing standard NATO rounds of the appropriate caliber. Most common in US are the M61 Armor piercing, M62 Tracer, and M80 Ball. For training purposes, M63 Dummy and M82 Blanks are used. The new tungsten cored M993 Armor-piercing rounds may also be fired in the M60 as well, though the did not enter the inventory until after the M60 was withdrawn from service in active-duty units.
When firing plants, the M13 or M13A1 blank-firing adaptor (BFA) is necessary in order to produce enough gas pressure to cycle the weapon with blanks. All ammunition must be fixed in a NATO standard M13 disintegrating metallic split-link belt to feed into the weapon.
The standard combat ammuniton mix for the M60 consists of four ball (M80) cartridges and one tracer (M62) in belts of 100 rounds. The four to one ration theoretically allows the gunner to accurately "walk" fire into the enemy. Tracer bullets do not fly quite the same trajectory as ball and the weapon's sights must be used for accurate fire- particularly at ranges in excess of 800 meters, where 7.62x51mm NATO tracer bullets usually burn out and are no longer visible. This is a problem for all weapons in this caliber using this tracer round.
When tested in the field, the M60 was fairly effective, but in the jungles of Southeast Asia in which it was soon used, the initial versions displayed several problems when used on the ground. A common complaint was the weapon's weight, though the M60 was among the lightest 7.62mm machine guns of the era. For units in Vietnam, the single most common complaint was that the M60 was comparatively unreliable and prone to jamming and other malfunctions, especially when it was dirty. Fine sand and dust in the mechanism could bring the M60 to a halt. This was a major factor in the Israeli Defense Force declining to adopt the M60 in favor of the FN MAG. The weapon was more difficult to cleas and maintain than the M1918 Browning Automatic Rifle (BAR) it replaced in the squad. In normal conditions it would often fire thousands of round without a serious jam, while
field conditions tended to reduce reliability without proper maintenance.
The safety was awkward to operate and worked the "wrong way" for soldier who were trained with the M16 rifle and M1911 pistol-that is, it required an upward movement of the thumb on the safety catch to make the gun ready to fire, rather than a downward movement as with other weapons. Additionally, it is possible to install parts of the fire control mechanism incorrectly, causing a "runaway gun'-meaning that it would keep firing until empty, even if the operator took his finger off the trigger.
The M60 sometimes tore rims off of fired cartridge cases during the extraction cycle, resulting in failure to remove the empty case, causing a jam that could take time to clear. The barrel latch mechanism (a swinging lever) could catch on the gunner's equipment and accidentally unlatch, causing the barrel to fall out of the gun. The lever was replaced with a push button mechanism, but many of the swinging-lever latches are still on guns in inventory, forty years after this problem was discovered.
The grip/trigger assembly is held in place with a rather fragile leaf spring clip instead of the captive pins used in other designs. The spring clip has been known to be prone to breakage since the first trials at Aberdeen Proving Grounds.
Several critical parts of early production M60s, such as the receiver cover and feed tray, were made from very thin sheet metal stampings and were prone to bending or breaking; sturdier parts were eventually available in the early 1970s. Early M60s also had driving spring guides and operating rods that were too thin and gas pistons that were too narrow behind the piston head, leading to problems with breakage.
Another criticism with some versions of the M60 is that the barrel was heavy. The bipd was a permanent fixture to the barrel as well as the gas chamber of the gas system; the latter was a result of using a piston design with a fixed regulator system. The non-adjustable front sight is fixed to the barrel, and adjustments for "zeroing" the sights could only be made at the rear sight, requiring re-adjustment when the barrel is changed-not ideal for combat situations. The bipod being attached to the barrel also meant that the weapon had to be put down on the ground for a barrel change, complicating the process unnecessarily, especially in combat situations.
There was no handle to hold the barrel by for changes. A large asbestos glove was part of the standard issue to allow the crew to handle hot barrels during barrel changes. Loss of the glove was always a problem.
The nomeclature M60 describes either the first adopted version or, generically, the family of weapons derived from it.
Major variantions include the M60E1, the M60E2, the M60E3, and the M60E4.
The M60C was adopted for use on fixed mounts on aircraft. It was characterized by the use of an electric solenoid to operate the trigger and a hydraulic system to charge the weapon. The M60D differed from the base model by employing spade grips, a different sighting system, and lacking a forearm. It was typically employed as a door gun on helicopters.
- T161: The M60's developmental designation before it was type-classified in the 1950s.
- M60: The basic model-type classified in 1957.
- M60E1: An improved version that did not enter production. The primary difference was the handle fixed to the barrel and the removal of the gas cyliner and bipod from the barrel assembly.
- M60E2: Used in vehicles as a coaxial machinel gun; electrically fired.
- M60B: Used in helicopters in the 1960s and 1970s; unmounted.
- M60C: Used in fixed mounts in aircraft in the 1960s and 1970s; electrically fired and hydraulically charged.
- M60D: Replaced the M60B; a pintle-mounted version used especially in armament subsystems for helicopters, but also in some other roles.
- M60E3: An updated, lightweight version adopted in the 1980s.
- M60E4 (Mk 43 Mod 0/1): An improved model of the 1990s that looks similar to the E3, but has many improvements. It has subvariants of its own, and is also use by the US Navy.
The initial version was officially adopted by the US Army in the late 1950s, though at this time it was only intended for the infantry. It was known as the T161 before it was adopted (specifically the T161E3), and was chosen over the competing T52 during testing in the 1950s.
The M60E1 was the first major variant of the original M60. it did not go into full-scale production, though many of its features were included into the later E3 and E4 variants. Some of its features were also incorporated into the existing
M60 production. This mainly changed how the gas cylinder, the barrel, and the bipod were connected; in the first iteration.
One of the more noticeable changes on the M60E1 is that the bipod attachment point was moved to the gas tube rather than the barrel (like on the later M60E3). It did not, however, have a forward pistol grip, as was added to the E3.
The M60E2 is used on armored fighting vehicles. It lacks many of the components of the standard M60, including stock and grips. The M60E2 was electrically fired, but had a manual trigger as a backup, as well as a metal loop at the back for charging. The gas tube below the barrel was extended to the full length of the weapon to vent the gas outside the vehicle.
The M60B was a short-lived version designed to be fired from helicopters, with limited deployement that was made in the 1960s and 1970s. It was not mounted, just held, and was soon replaced by the pintle-mounted M60D. It had a different rear stock than the regular model, and still had a pistol grip (as opposed to spade grips). The M60B's advantage over pintle-mounted variants was that it had a wider and much less restricted field of fire.
The M60C is a variant of the standard M60 for aircraft-mounting, such as in helicopter armament subsystems. It lacks things like the bipod, pistol grip, and iron sights. The main difference between the standard M60 and the "C" variant is the electronic control system and the hydraulic swivel system used. It could be fired from the cockpit by the pilot or copilot. It is an electronically controlled, hydraulic-powered, air-cooled, gas-operated, belt-fed weapon system. It used the M2, M6, and M16 armament subsystems.
The M60D is a mounted version of the standard M60. It can be mounted on boats, vehicles, and as a pintle-mounted door gun in helicopters. When used in aircraft, it differed from the M60C in that it is not controlled by the pilot-rather, it is mounted in a door and operated by a member of the crew. Like the rest of the M60 family, it is an air-cooled, gas-operated, belt-fed weapon. Unlike the other models, however, the M60D normally has spade grips and an aircraft ring-type sight or similar, as well as an improved ammunition feed system. A canvas bag is also affixed to the gun to catpture ejected casings and links, preventing them from beiing sucked into the rotor blades or into an engine intake. The M60D was equipped on the UH-1B Huey, the CH-47 Chinook, the ACH-47A "Guns-A-Go-Go" version of the Chinook, and on the UH-60 Blackhawk.
The M60E3 was fielded c. 1986 in an attempt to remedy problems with earlier versions of the M60 for infantry use. It is a lightweight, "improved" version intended to reduce the load carried by the gunner. Unlike its predecessors, the M60E3 has several updated modern features. It has a bipod for improved stability, ambidextrious safety, universal sling attachments, a carrying handle on the barrel, and a simplified gas system. However, these features also caused almost as many problems for the weapon as they fixed. There were different types of barrels used, but the lightweight barrel was not as safe for sustained fire at 200 rounds per minute as heavier types. However, some personnel claim to have witnessed successful prolonged firing of the weapon. The stellite superalloy barrel liner makes it possible, but the excessive heat generated by this process can quickly make the gun unusable. There were two main barrels, a lightweight barrel and another heavier type-the former for when lighter weight was desired, and the latter for situations when more sustained fore was required.
The reduced weight components also reduced the durability of the weapon, amaking it more prone to rapid wear and parts breakage than the original. Most infantry units in the US Army and Marine Corps have now switched to the M240 as their general-purpose machine gun, which is more reliable (particularly when dirty) and seems to be well liked by the troops for its ruggedness, despite the fact that it weighs 27.6 lb compared to the standard M60 at 23.5 lb.
Scaled down derivatives of the M60 machine gun also existed as the Ford Aerospace XM234 and Rodman Laboratiories as a replacement for the M1918 Browning Automatic Rifle. Both weapons lost to the FN Minimi.