A light machine gun (LMG) is a machine gun designed to be employed by an individual soldier, with or without an assistant, as an infantry support weapon. Light machine guns are often used as squad automatic weapons.
Modern light machine guns often fire smaller-caliber cartridges than medium machine guns, and are usually lighter and more compact. However a light machine gun is defined by its usage as well as its specifications: some machine guns - notably general-purpose machine guns - may be deployed either as a light machine gun or a medium machine gun. Deployed with a bipod, and firing short bursts it is a light machine gun; if deployed on a tripod and used for sustained-fire it is a medium machine gun.
It is possible to fire a light machine gun from the hip or on the move as a form of suppressive fire intended to pin down the enemy. Marching fire is a specific tactic which relies on this capability. Otherwise, light machine guns are usually fired from a prone position using a bipod.
Many light machine guns (such as the Bren gun or the M1918 Browning Automatic Rifle) were magazine-fed. Others, such as the MG 34, could be fed either from a belt or a magazine. Modern light machine guns are designed to fire more rounds of a smaller caliber and as such tend to be belt-fed. Some LMGs, such as the Russian RPK, are modifications of existing assault rifle designs. Adaptations generally include a larger magazine, a heavier barrel to resist overheating, a more robust mechanism to support sustained fire and a bipod. Other modern light machine guns, such as the FN Minimi, are capable of firing from either an ammunition belt or a detachable box magazine. Lighter modern LMGs have enabled them to be issued down at the fireteam level and at two or three at the section/squad.
Light machine guns were first introduced in World War I to boost the firepower of the infantry. By the end of World War II, light machine guns were usually being issued on a scale of one per section or squad, and the modern infantry squad had emerged with tactics that were built around the use of the LMG to provide suppressive fire.
The following were either exclusively light machine guns, had a light machine gun variant or were employed in the light machine gun role with certain adaptations.
- Degtyaryov light machine gun (7.62x54mm R)
- Browning Automatic Rifle (.30-06 Springfield, 6.5x55mm, 7.92x57mm Mauser)
- Type 99 Light Machine Gun (7.7x58mm Arisaka)
- FN Minimi (5.56x45mm NATO)
- M249 Squad Automatic Weapon (5.56x45mm NATO)
- Mk 48 machine gun (7.62x51mm NATO)
- CETME Ameli (5.56x45mm NATO)
- Ultimax 100 (5.56x45mm NATO)
- Vektor SS-77
- IMI Negev (5.56x45 mm NATO)
- Ares Shrike 5.56 (5.56x45 mm NATO)
- Stoner LMG (5.56x45 mm NATO)
- Colt Automatic Rifle (5.56x45 mm NATO)
- Heckler & Koch MG4 (5.56x45 mm NATO)
- Steyr AUG (5.56x45 mm NATO)
- Nikonov machine gun (5.45x39mm)
- L86 LSW (5.56x45 mm NATO)
- Heckler & Koch MG36 (5.56x45 mm NATO)
- INSAS LMG (5.56x45 mm NATO)
- SAR-21 LMG (5.56x45 mm NATO)
- EMERK (5.56x45 mm NATO)
- Pecheneg machine gun (7.62x54mmR)