From World War One through the Korean War, the standard US service cartridge was the “US Cartridge, Caliber .30, Model of 1906,” commonly known as the .30-06 Springfield. The cartridge was long (3.34") and required a standard length action to handle it.

Designers learned that by shortening the case by roughly half an inch and loading to higher pressure, they could equal the performance of the 30-‘06 yet make weapons shorter and lighter. Thus was born the 7.62x51mm NATO round. With ballistic performance identical to the older .30-06 cartridge, the new .30 caliber round has a muzzle velocity of about 2,800 feet per second with a 150 grain bullet and an effective range of 500+ yards. A civilian version of this cartridge, the .308 Winchester, was actually adopted before the militray version and has been very popular for sporting use.

America’s first machine gun designed to fire the new cartridge was the M60 General Purpose Machine Gun, built by Marmont in Saco, Maine. The weapon feeds from 100-round linked metal belts of ammo loaded from the left side.

It fires from the open-bolt, meaning that when the operator pulls the trigger, the spring-loaded bolt flies forward, pushing a live cartridge from the link and into the chamber. The round fires as soon as the breech is closed. Before the bullet leaves the barrel, tapped gas from the burning gunpowder unlocks the action and pushes the bolt back, compressing the recoil spring and at the same time extracting and ejecting the fired case. The bolt then flies forward again, loading and firing another live round from the belt. This cycle repeats continuously as long as the operator holds back the trigger. There is no provision for semi-auto fire. The gun fires only on full-automatic, but the rate of fire is relatively slow at 550 rounds a minute and a skilled operator can learn how to squeeze off single shots.

The M60 has a bipod permanently attached to its barrel that is useful in firing from the prone position. The weapon can also be attached to a pintle mount or mounted on a tripod.

The M60 machine gun weighs 23 pounds. By comparison, the Browning Automatic Rifle (BAR) weighed 19 pounds, the M1917 MG weighed 32 pounds and the M1919 MG weighed 31 pounds. The M60 replaced all of these weapons in U.S. military service.

While the other U.S. armed services have recently replaced the M60 with the 7.62x51mm M240 (designed by FN of Belgium) the US Navy continues to field the M60. It is currently employed throughout the fleet in the shipboard security role.