M60 machine gun
The M60, officially the Machine Gun, Caliber 7.62 mm, M60, is a family of American general-purpose machine guns firing 7.62×51mm NATO cartridges from a disintegrating belt of M13 links. There are several types of ammunition approved for use in the M60, including ball, tracer, and armor-piercing rounds.
It was adopted in 1960 and issued to units later that year. It has served with every branch of the U.S. military and still serves with the armed forces of other nations. Its manufacture and continued upgrade for military and commercial purchase continues into the 21st century, although it has been replaced or supplemented in most roles by other designs, most notably the M240 machine gun in U.S. service.
Overview
The M60 is a belt-fed machine gun that fires the 7.62×51mm NATO cartridge, which is commonly used in larger rifles, such as the M14. The gun's weight and the amount of ammunition it can consume when firing make it difficult for a single soldier to carry and operate, so it is generally used as a crew-served weapon, operated by a team of two or three individuals. The team consists of the gunner, the assistant gunner, and the ammunition bearer. The gunner carries the weapon and between 200 and 1,000 rounds of ammunition depending on strength and stamina. The assistant carries a spare barrel and extra ammunition and reloads and spots targets for the gunner. The ammunition bearer carries additional ammunition and the tripod with associated traversing and elevation mechanism and fetches more ammunition as needed during firing.The M60 can be accurately fired at short ranges from the shoulder thanks to its design. This was an initial requirement for the design and a hold-over in 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 uses the M13 ammunition link, a change from the older M1 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 from 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 has been adopted by various military agencies around the world. It also has been updated and modernized throughout the years to meet modern military requirements.
History
The M60 machine gun began development after World War II as a program for a new, lighter 7.62 mm machine gun. This weapon was intended to replace the aging inventory of Browning M1919 machine guns. It drew inspiration from the German "universal machine gun" concept which attempted to create a single weapon to take over the roles of several different categories of machine gun. The MG-34 and later MG-42 could be carried and used from the shoulder like a typical light machine gun, but could also handle sustained fire as a crew served emplaced weapon or mounted on a vehicle.During the Second World War, the US army's interest in the MG 42 led them to order the construction of two test copies of the gun in 30.06 Springfield, to evaluate the potential of copying the German gun directly. These were designated the T24, and trials were undertaken at Aberdeen, where the weapon was found to be unsatisfactory.
Postwar, the program that would eventually lead to the M-60 started with the creation of a proof of concept light machine gun, which was contracted to the Bridge Tool and Die company. A captured German FG-42, which was a lightweight light machine gun intended for use by paratroopers, was modified to be belt fed by installing the top cover from an MG-42 onto the left side of the gun and making extensive changes to the receiver to support its function. A single example gun was constructed in 1946 which became known as the T44. After testing, the army identified a number of attributes they wanted the new machine gun to have, such as disintegrating links and a quick change barrel.
As development continued, a new pattern of gun was built from the ground up, which was designated the T52. This gun retained the more successful elements from the T44, including the MG-42 derived top cover and a similar bolt and carrier. It also incorporated interchangeable barrels, disintegrating link belt, and was now chambered in the new 7.62x51mm cartridge. Compared to the T44, the feed was moved to the top and the design was strengthened to better support sustained fire. The final evaluation version was designated the T161E3. It was intended to replace the M1918 Browning Automatic Rifle and M1919A6 Browning machine gun in the squad automatic weapon role, and in the medium machine gun role. It was accepted as the M60 in 1957, over foreign competitors primarily consisting of the Belgian FN MAG.
Vietnam War
Many U.S. units used the M60 during the Vietnam War as a squad automatic weapon. 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 added two M60 gunners beside the main.50-caliber machine gun while the Patrol Boat, River had one in addition to two.50-cal mounts.The M60 received the nickname "The Pig" due to its bulky size and appetite for ammunition. Vietnam's tropical climate harshly affected weapons, and the M60 was no exception. Its light weight led to it being easily damaged and critical parts like the bolt and operating rod wore out quickly. Even so, soldiers appreciated the gun's handling, mechanical simplicity, and effective operation from a variety of firing positions. United States Navy SEALs used M60s with shorter barrels and no front sights to reduce weight. Some SEALs had feed chutes from backpacks to have a belt of hundreds of rounds ready to fire without needing to reload.
Many incidents demonstrated the effectiveness of the M60 in combat. In 1966, Medal of Honor recipient Lance Corporal Richard Pittman, a Marine with 1/5, used the M60 to engage superior elements of the 324th North Vietnamese Army Division, defeating two enemy machine gun positions and suppressing enemies in his immediate vicinity, then advancing another 50 meters into the face of more attacking NVA.
In the 1980s, the Army partially replaced the M60 by the M249 Squad Automatic Weapon within infantry squads. Their new doctrine reduced the general-purpose machine gun role in favor of portability and a greater volume of fire. However, many disliked the M249, which was less reliable, accurate, and long-ranged, and fired a 5.56 mm round that was lighter than the M60's 7.62 mm round. The M60 was retained in the vehicle-mounted and the general-purpose roles due to its greater power and range.
The U.S. Marine Corps, which became concerned about the M60's reliability, weight, and the high round counts, adopted the M60E3 to replace most original M60s in infantry units. The M60E3 was five pounds lighter than the original M60. It included a forward pistol grip and had the bipod mounted to the receiver rather than the barrel. The weapon still was not durable and its performance was reduced.
In the early 1990s, Saco Defense addressed Navy Special Warfare requirements to develop a retrofit parts package for the machine gun. Called the M60E4, it was more reliable and durable than the M60E3, had a "duckbill" flash suppressor, and a shorter and thicker positive lock gas cylinder extension. The first NAVSPECWAR units received it in late 1994, when it was designated the Mk 43 Mod 0.
File:Spops2004afghanm60.jpg|thumb|A 19th Special Forces Group soldier mans an M60 machine gun on a Humvee in Afghanistan in March 2004. An AT4 anti-armor recoilless gun can be seen in the foreground.
In January 1994, the U.S. Army began the Medium Machine Gun Upgrade Kit program. The only two competitors were M60 and M240 versions. Saco offered an "enhanced" M60E3 with improved parts, and FN offered the M240 variant of its MAG; both weapons were upgrade kits of weapons already in service. Eighteen guns of each were tested until December 1995. There were two main performance areas: mean rounds between stoppages and mean rounds between failures. 50,000 rounds were fired through both guns. The M240 had 2,962 MRBS and 6,442 MRBF, compared to the M60's 846 MRBS and 1,669 MRBF. As a result, the M240 was declared the winner and accepted into infantry service. Although the M60 was lighter, had better balance, was more controllable, and there were many in the inventory, it did not work reliably enough. Starting with Ranger battalions, the U.S. Army began adopting and modifying M240 variants to replace their remaining M60s in the early 1990s.
The M60, though largely phased out, continued to be used in the 21st century by U.S. Navy SEALs. It was the main 7.62 mm machine gun used by some U.S. special operations forces to the late 1990s. As of 2005 it was used by the U.S. Coast Guard, U.S. Navy, and some reserve units.
In 2015, the Danish Army adopted an M60E6 variant from U.S. Ordnance to replace their aging MG3s in infantry roles.
Design
The M60 is a gas-operated, air-cooled, belt-fed, automatic machine gun that fires from the open-bolt position and is chambered in 7.62×51mm NATO. It has a cyclic rate of fire of around 500–650 rounds per minute. Ammunition is usually fed into the weapon from a 100 or 250-round disintegrating, metallic split-link belt.The final design features a quick change barrel to help manage heat during sustained fire. It is fully automatic only. The operating system is a derivation of the one used in the FG-42, which itself was derived from earlier Lewis light machine guns. The operating rod locks and unlocks the rotating bolt via a cam track and also doubles as a linear hammer to fire the gun. It's held back by a simple dropping sear in the fire control group. The belt feed system is similar to the MG-42 and cartridges are pushed forward out of the belt directly into the chamber, unlike the Browning M1919 which pulled cartridges out of the rear of the belt first.
The M60 was developed in parallel with the M14 service rifle and both guns used a very similar gas system. This gas cut off/expansion design was intended to increase the gun's tolerance to differences in ammunition, and worked by feeding gas into holes in a hollow piston which were cut off the moment the action started moving. In this way the hot gasses would drive the cycling of the gun through their continued expansion inside the gas block, and the amount of gas let in would depend on the pressure inside the barrel, creating a self regulating effect. This design carried the accidental possibility that the gas piston could be installed backwards when the gun was stripped for cleaning. In this state, the weapon could chamber a round and fire, but would not cycle.
File:030104-N-7676W-058 - M60E3 live fire exercise.jpg|thumb|left|A navy sailor fires an M60E3 machine gun during a live-fire exercise at the Mobile Inshore Underwater Warfare Site at Guantánamo Bay, Cuba in 2003.
The M60 was designed to be able to be effectively fired from the shoulder, hip, or underarm positions. However, to achieve the maximum effective range, it was primarily intended that the weapon be employed from a bipod or a tripod, and the gun fired in bursts of 3–5 rounds.
The M60 is often used with its own integrated bipod or with the M122 tripod. The M60 is considered effective up to 1,100 meters when firing 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. United States Marine Corps 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.