ZPU-4

The ZPU-4 is an anti-aircraft gun used in Call of Duty 4. It is one of the most prolific anti-air defenses in the world, with dozens of users all across the globe, with single and double barreled versions known as the ZPU-1 and ZPU-2 respectively, though only the four-barreled version is seen in the game.

Description
The ZPU-4 is derived from the Soviet KPV 14.5mm Machine Gun and first entered Soviet service in 1949. The quad version is mounted on a four-wheeled carriage with two legs that extend when the vehicle is ready to fire within 15-20 seconds, although the weapon can be fired in 'travel mode' without the stabilizing legs extended. It can fire a variety of ammunition. It has a firing rate of about 600 RPM for each barrel, but has only a practical firing rate of about 150 RPM.

History
The ZPU-4 has been used in a variety of conflicts since the end of the Second World War, first by Chinese and North Korean forces in the Korean War. It was later used in a variety of subsequent wars, including the Vietnam Conflict and Desert Storm. Although obsolete against most low-flying airplanes, it has proven to be quite effective against helicopters. Despite this, in many areas it has been replaced with the newer, more powerful ZU-23. It has also been mounted on vehicles.

Call of Duty 4
The ZPU-4 is used by OpFor forces in the Middle East during the invasion of a small Middle Eastern nation under the control of Al-Asad. During the mission The Bog, Paul Jackson is tasked with destroying a ZPU-4 in order to allow AH-1 Cobra helicopters to come in and secure the area to rescue a stranded tank, War Pig.

It is most likely that tens of other ZPU-4s are firing throughout the mission Bog and multiplayer level of the same name. They usually fill the night, firing at the skies above, though the player does not see much aircraft going about. In the mission Shock and Awe, ZPU-4s will fire at Paul Jackson while he is using the Mk 19.

Call of Duty: Modern Warfare 2
The ZPU-4 appears in the level Exodus, where it is being used by Russian paratroopers to destroy American air support. The player must destroy them by telling artillery where the ZPUs are.

A few can also be found on the multiplayer map Afghan. Also in the mission "The Gulag" as your giving Mactavish sniper support after he says shift right once you can see blue tarp. Under that is a ZPU-4. People will be uncovering it. But, if you kill the people uncovering it, the tarp will be removed anyway.

Trivia
Interestingly enough the soldiers operating the ZPU-4's in Exodus are capable of dying to head shots, stopping the operation of the ZPU's, but you are still required to call in a artillery strike on them.