Call of Duty: Modern Warfare: MobilizedEdit
It is almost a copy of the M16A4 found in Call of Duty 4: Modern Warfare. Notable differences are that the 3-round burst has a slower rate of fire, more compact iron sights, and a smaller delay between the bursts.
In the campaign, the M4 Carbine is exclusive to the level "Closing In", though it can be seen in use by allies in all the missions of the American campaign. It produces the same sound as the M4A1, but it has a lower damage per bullet, still killing with one burst. Due to its 3-round burst and only extra 120 rounds that come with it, the M4 is the least ammunition efficient weapon.
In multiplayer, the M4 Carbine is available by default, along with the MP5 and MP7. It is probably the least common weapon used in multiplayer, due to its lack of power, as it takes two bursts to kill, and low ammunition efficiency. Those who do use it usually discard it when the M4A1 is unlocked, since it has much higher power and the same rate of fire as the M4 Carbine, only without the delay between bursts.
Call of Duty: Modern Warfare 3: DefianceEdit
The M4 returns in Call of Duty: Modern Warfare 3: Defiance, this time, as a fully automatic assault rifle.
The US National Guard are often equipped with this. In the campaign, on various missions the player often starts off equipped with the M4, and later in the game the M4 can be picked up with various attachments. Unlike its Mobilized counterpart, the M4 is now fully-automatic with a high rate of fire, penetration and average recoil.
- Scope - Unlocked at 150 kills with standard M4.
- Red Dot Sight - Unlocked at 150 kills with Scoped M4.
- Grenade Launcher - Found in multiplayer maps as a pop up "Mystery Weapon", if enabled.