The M60 is a general purpose machine gun designed in the USA. It was originally introduced to service in 1957 and is still in service with some branches of the US armed forces. The M60 machine gun fires the 7.62x51mm round (commonly referred to as .308, though 7.62x51mm NATO has a slightly different neck) and fires from a disintegrating belt. People familiar with the weapon, most commonly members of the armed forces during Vietnam, frequently refer to the M60 as "the hog". The M60 is a heavy weapon, weighing over 20lbs. The M60 is gas operated and fires from the open bolt position. To help keep lead flying towards the enemies, the air-cooled barrel is setup to be quickly removed without risking injury to the operator by means of a glove that was issued along with the weapon. Because the bipod was mounted to the barrel, and there was no handle on the barrel, sometimes barrel changes were awkward. Also, losing the glove meant that some alternate method of protection from the heat of the barrel had to be sought out. However, this quick change barrel aides in keeping more rounds on target without having to wait for the barrel to cool, or risking failure due to extreme heat.
The M60 is generally used by a crew of at least 2 men, not by one individual person as is often seen in movies such as Rambo. Generally, in addition to the gunner there will at least be someone there to assist him by carrying the ammunition. The weapon can be fired from the shoulder if needed, though this is not optimal. It is usually seen with a forward mounted bipod, although a tripod was also designed for the weapon.
Most of these weapons have been replaced by the newer, lighter, and slightly easier to use M249. Although many units (especially vehicle crews) prefer the M60 for it's advantages in range and stopping power over the M249. The M249 uses the standard 5.56mm round, which is significantly smaller than the 7.62x51mm round.
It is recommended to fire the M60 in short bursts of 3-5 rounds, as opposed to long streams of fire. The heavy, powerful 7.62x51mm round produces a lot of recoil, and after a 3-5 round burst accuracy greatly diminishes, resulting in wasted ammo and reducing the number of targets that can be successfully engaged.
Initially, there were several problems with the gun including reliability issues such as FTE (failure to extract), barrels falling off, pins breaking, damage due to the possibility of installing components of the fire control group incorrectly, and bending/breaking components of the stamped sheet metal receiver. There have been many variants of the M60 to help remedy some of these problems. The most well known variants of the M60 are the standard M60 (first run), the M60E3 (which was created in the 1980s), and the most recent version, the M60E4 (produced during the 1990s). The M60E4 is generally the one seen in video games (such as the Call of Duty Modern Warfare series), fitted with rails and other modern commodities.
It is interesting to note that a fully automatic M60 costs the US military around $6000, but a semi automatic civilian version (if you can find them) costs two to three times that amount. However, civilians in the United States can obtain parts kits and assemble their own with the proper licensing (FFL class II manufacturer's license). Most fully automatic M60s seen in the civilian world are assembled by class II manufacturers.