The M4A1 a lightweight, gas operated, air-cooled, magazine fed, select-fire rifle that is used by all branches of the United States military as a standard offensive and defensive small-arm, as well as several other of the world's armed forces in a number of variants. The rifle is chambered for the 5.56x45mm NATO cartridge (which means that it can fire the relatively common .223 remington round as well) and boasts a cyclic rate of about 800 rounds per minute. Derived from the M16 rifle, the M4A1 is significantly lighter and shorter than its predecessor and is usually equipped with a collapsible stock and a 14.5" barrel. The rifle has a maximum effective range of 600 meters, though it was primarily designed for engagements at 200 meters and under. Like the M16, the M4A1's qualities lie in its user-friendliness, ease of functionality, and lack of complexity. Generally, a user will only need to access about three to four of the weapon's components during a routine maintenance. The weapon is also praised for its accuracy and its low recoil. This benefits the user in several ways: aimed fire will have a higher likelihood of striking a target and the reduced felt recoil affords the shooter the luxury of accurate and more rapid follow-up shots when engaging multiple hostiles. The one drawback of M4A1 weapon system is its maintenance schedule. The rifle must be cleaned regularly as the direct-impingement gas system which operates the weapon creates fouling which was learned during Vietnam to reduce performance and cause misfires.

If you fired this rifle at a zombie's head and it will easily pentrate the skull and cause severe trauma to the brain, killing or incapacitating the zombie. In the event of a global, Earth-changing zombie apocalypse, acquiring an M4A1 will be a fairly effortless task, since it is used the military and most police departments in the United States, both of which would be defunct institutions at this point. In addition, if you are a civilian and own an AR-15 rifle, the M4A1 shares with it a 90% component commonality, as well as being capable of accepting the same ammunition and magazines. The weapon also accepts a number of accessories, such as scopes, laser designators, taclights, and can mount the Masterkey, M203, and suppressors. (On the other hand, it'll be nice if you can find a Century Magazine/C-Mag for it; its 100-round capacity would help a lot during the Zombie apocalypse, plus being lighter than a light machine gun. Be warned that such a heavy magazine has the potential to cause problems with the magazine retention which can make reloading problematic.)