A Light Machine Gun, often abbreviated as LMG, is a type of weapon in the Call of Duty series. Light machine guns carry high amounts of ammo in their magazines (typically 100, but not always the case), allowing them to be fired for extended periods of time.
The drawbacks of light machine guns are that they are heavy, making the player carrying them move much slower than when using other guns. Reload times are generally longer than with any other weapon group as well. Hip-fire is also very inaccurate, and it takes more time to aim down the sights than submachine guns or assault rifles, making Light Machine Guns at a disadvantage in close-quarters combat. They are best used for support and while stationary, rather than offensively. The "Overwatch" tactic involves using a Light Machine Gun from an elevated area to support teammates below.
Compared to Heavy Machine Guns, Light Machine Guns do more damage but hold less ammo. In games without Heavy Machine Guns, this is not the case. With the release of Call of Duty: 'Modern Warfare 3, one notable thing to be said is that if one uses the Attachments Proficiency with a grip and an ACOG scope, the machine gun will remain fairly accurate in most cases, which is quite the opposite of its predecessor Call of Duty:Modern Warfare 2, where using such a setup would result in heavy uncontrollable recoil. Additionally, going prone with LMGs in Call of Duty: 'Modern Warfare 3 reduces recoil to minimal amounts, allowing for any LMG to fire its entire magazine while staying on target from a considerable distance. Some LMGs use magazines, these are much quicker at reloading than the other weapons in the category and allow players to maintain firing with less concern of having to find a safe location to reload.
The RPD and the M240 were planned to be in Modern Warfare 3 but were scrapped before the release of the game. However the M240 can be seen in the "No Russian" flashback in "Blood Brothers".