The gun's weight and the amount of ammunition it can consume when fired make it difficult for a single soldier to carry and operate.

It was partly derived from German guns of World War II (most notably the FG 42 and the MG 42),[11][12] but it contained American innovations as well.

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.

Its light weight led to it being easily damaged and critical parts like the bolt and operating rod wore out quickly.

In 1966, Medal of Honor recipient Lance Corporal Richard Pittman, a Marine with 1/5 (1st Battalion/5th Marine Regiment), used the M60 to engage superior elements of the 324th North Vietnamese Army (NVA) 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.

[17] 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.

[17] 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.

[citation needed] 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.

The design drew on many common concepts in firearms manufacture of the period, such as stamped sheet metal construction, belt feed (a modified mechanism for belt feed from the MG 42 with a single pawl), quick barrel replacement, a pistol grip and stock, and a semi bullpup design similar to the FG 42 (much of the action occupies the weapon's stock).

[17] 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.

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.

At the time of the M60's development, other designs, like the Belgian FN MAG and the German Rheinmetall MG 3 (MG42 derivative), had yet to enter production.

In Army tests, the M60 proved fairly effective, but in the jungles of Southeast Asia, it displayed a number of troubling issues.

The single most common complaint was that the M60 was unreliable in extreme conditions and prone to jamming and other malfunctions during heavy firing, especially when it was dirty.

Sometimes spent casings would fail to extract and stay stuck inside the chamber, forcing a barrel change before it could be fired again.

[22] Due to the rotating bolt design, the M60 required stoning of burrs or roughness on the lugs, which could increase headspace, occasionally causing cartridge case stretching and head separation.

On new M60s, the lever was replaced with a push button mechanism that was less likely to be accidentally released, but few of the older M60s were modified due to expense, with many of the extant weapons still bearing them.

An unusual arrangement of the M60B was done by HA(L)-3 squadron aircrew by removing the sights, shortening the barrel inline to the gas block, removing the stock to shorten the receiver as the shorter buffer spring increased the rate of fire, an improvised side mounted grip was installed on the handguard.

This arrangement allowed the door gunners easier movement of the weapon as well as firing sideways improved the belt feed performance.

Unlike 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 capture ejected casings and links, preventing them from being sucked into the rotor blades or into an engine intake.

The stellite superalloy barrel liner makes it possible, but the excessive heat generated by this process may quickly render the gun unusable.

The reduced-weight components also reduced the durability of the weapon, making it more prone to rapid wear and parts breakage than the original.

All USAF M60E3s were withdrawn from general issue by 1990, because it did not meet the vehicle mount requirements of the Cadillac Gage Ranger and due to overheating problems.

The M60E3 did remain in the Air Force as weapons converted back to M60 configuration with the E3 X-stamped via locally installed kits issued from depot.

It was developed for the U.S. Navy SEALs to replace their existing stock of M60E3 machine guns fitted with shorter "assault barrels".

The adjustable front sight allows for zeroing of the primary and spare barrel, the chrome and induction hardening lengthens service life, and the ammunition is now mounted on the receiver, preventing damage, and thereby feed failure.

The machine gun's light weight—20 to 21 pounds (9 to 10 kilograms)—and compact design make it easy to carry long distances and maneuver in tight spaces.

If the design is approved by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE), they are treated as belt-fed semi-automatic rifles; however, individual state and local regulations still apply.