The M240, formally United States Machine Gun, 7.62mm, is a family of belt-fed, gas operated medium machine guns firing the 7.62x51mm NATO cartridge (w/ M13 Link). It is the US designation for the Belgian FN MAG 58 machine gun.

The M240 has been used by the United States armed forces since the late 1970s. It is used extensively in a dismounted role by infantry units, and is also mounted in ground vehicles, watercraft, and aircraft. Despite not being the lightest medium machine gun in service, the M240 is highly regarded for reliability, and its standardization among NATO members is also seen as a major advantage.

Variants:

All variants of the M240 series are fed from disintegrating belts, and are capable of firing most types of 7.62 mm NATO ammunition. All variants of the FN MAG 58, including the M240, can use European-type non-disintegrating belts (following replacement of a few easily-swappable parts). They all share the same basic internal parts, which are also interchangeable, for the most part, with other members of the FN MAG family. There are significant differences in weight and some features among some versions for which this does not apply. The M240 is manufactured by the American division of FN Herstal, a Belgian company with historically deep ties to U.S. arms procurement.

Loading the weapon is performed by pulling the charging handle which locks the bolt to the rear. The weapon is placed on safe and the charging handle is pushed forward (this is spring loaded on the tank mounted version). The feed tray cover is then lifted and rounds are laid inside the feed tray. The feed tray cover is then closed and the weapon is ready for operation.

Clearing the Weapon

Clearing the weapon is performed by ensuring the bolt is locked to the rear and the weapon is on safe. The feed tray cover is then lifted, the remaining belt (if any) is swept out of the feed tray, the feed tray is lifted to visually inspect the rear of the barrel and the face of the bolt. Any links or brass casings are removed. The weapon is now clear. In the unlikely event that a live round is on the bolt face, it is knocked loose with a cleaning rod or another rigid object. If there is a live round lodged in the barrel, the operator must immediately decide if the barrel is hot enough that there is a chance of it cooking off. If there is, he will immediately move his face away from the opening of the weapon. He should then wait for the barrel to cool off before attempting to remove it. In many cases, attempting to remove the barrel will cause the round to detonate as soon as the barrel is unlocked from the receiver. He can also attempt to extract the round by taking the weapon off of safe, pulling the trigger and pulling back on the charging handle. This has a fair chance of causing the weapon to fire, so care should be made in ensuring that the weapon is pointed in a safe direction first.

Rate of Fire

The rate of fire may be controlled by three different settings. The first setting allows the weapon to cycle at 750 round/min. The two remaining settings increase the rate of fire by 100 round/min per setting second setting being 850 round/min and third setting, 950 round/min). These settings are changed by dismounting the barrel, removing the gas regulator collar and turning the gas regulator to allow more or less gas to move through the weapon system. It is generally performed before missions, as changing the setting is distracting at best under field or combat conditions.

Changing Barrels

The barrels can be exchanged rapidly, thanks to a barrel release button located on the left side of the weapon. The weapon is cleared first and then the button is held down, while the barrel's carrying handle is moved from the right side of the weapon to the center, unlocking it from the receiver. At this point, the button is released and the barrel is then pulled free of the receiver and placed to the side. The new barrel is inserted into the receiver and then the carrying handle is shifted to the right, locking it into place.

During prolonged firing, care must be taken to not allow exposed skin to come in contact with the weapon. The barrels can become hot enough to inflict second degree burns instantly without becoming visibly different. However, such barrels glow brightly to anyone using any sort of optics sensitive to infrared radiation, such as night vision devices.
(Content extracted from Wikipedia)

Specifications: