M60 GPMG

Development of the M60 began after the Second World War as a program for a lighter machine gun to replace the Browning M1919 series. American interest in the German "universal machine gun" concept led the Army to order two MG 42 copies chambered in .30-06, designated the T24, which were judged unsatisfactory at Aberdeen Proving Ground. Postwar work resumed with a proof-of-concept gun contracted to the Bridge Tool and Die Company: a captured FG 42 fitted with an MG 42 top cover mounted on its left side, built as a single example in 1946 and known as the T44. Requirements for disintegrating links and a quick-change barrel led to a new gun built from the ground up, the T52, and then to the T161E3, which was selected over the T52 and the Belgian FN MAG. The design was type-classified as the M60 in 1957 and issued from 1960, replacing the M1918 BAR and the M1919A6.

The M60 is gas-operated, air-cooled and belt-fed, firing from an open bolt in fully automatic mode only from M13 disintegrating split-link belts. The operating system derives from the FG 42, itself descended from the Lewis gun: the operating rod locks and unlocks the rotating bolt through a cam track and doubles as a linear hammer, held by a dropping sear in the fire control group. The belt feed follows MG 42 practice, pushing cartridges forward out of the links directly into the chamber. The gas system, developed in parallel with the M14 rifle, uses a cut-off and expansion principle in which gas entering ports in a hollow piston is sealed off once the action begins to move, giving self-regulation across ammunition lots; the piston could be reassembled backwards, allowing the gun to fire but not cycle. Barrels are stellite-lined and quick-change. Firing from the shoulder, hip or underarm was a design requirement, with the integral bipod and M122 tripod used for aimed fire. Recurring faults included a poorly balanced carry, jamming when fouled, torn case rims, headspace growth from bolt lug burrs, an accidentally released barrel latch lever later replaced by a push button, a fragile leaf spring clip retaining the grip assembly, and sear wear causing runaway fire, addressed by a second sear notch.

The M60 served with every branch of the U.S. military and saw heavy use in Vietnam, where it was nicknamed "The Pig." SEALs cut down barrels and removed front sights, and some used backpack feed chutes. The M249 partly displaced it in Army squads during the 1980s. Variants include the M60E1, which did not enter production; the M60E2 coaxial gun for the M48A5, M60 Patton and K1 Type 88; the helicopter-fired M60B; the M60C for fixed aircraft mounts on the OH-13, OH-23, UH-1B and OV-10; the pintle-mounted M60D; the Rock Island CAR60 kit of 1983; the lightened M60E3, fielded around 1986; and the M60E4, adopted by the Navy as the Mk 43 Mod 0/1 from late 1994. Following Army trials from 1994 to 1995, the M240B replaced it in infantry service. U.S. Ordnance has produced the Mk 43 since 2000. The M60E6 won the Danish Army's replacement program in March 2014, with deliveries from 2015. Users include South Korea, which produced it under licence from 1974, Taiwan, Indonesia, Portugal, the Royal Air Force, and the Los Angeles Police and Sheriff's Departments.