M21

The M21 Sniper Weapon System (SWS) is the semiautomatic sniper rifle adaptation of the popular M14 rifle. It is chambered for the 7.62x51mm cartridge.

The United States Army wanted an accurate sniper rifle during the Vietnam War. The M14 was selected because of its accuracy, reliability, and the ability for a quick second shot. As a result, in 1969, the Rock Island Arsenal converted 1,435 National Match (target grade) M14 rifles by adding a Leatherwood 3–9x Adjustable Ranging Telescope telescopic sight and furnishing National Match grade ammunition. It was designated the XM21 until 1975, when it became the M21.

The M21 remained the Army's primary sniper rifle until 1988, when it was replaced by the bolt-action M24 Sniper Weapon System. While bolt action rifles are generally more accurate at long distances (1000 m) than semi-automatic weapons, semi-automatic rifles are more than adequate for medium distances (600 m), and its higher rate of fire makes it an ideal designated marksman's rifle (DMR). The M21 remains in the inventory of the Army National Guard, though it has mostly fallen out of use.

In Game
In single-player, the M21 is found in two versions, regular and suppressed. The regular version is found in One Shot, One Kill and Heat. The suppressed version is found in Blackout and All Ghillied Up.

The M21 can be unlocked in Call of Duty 4 multiplayer at level 7. It is the second sniper rifle obtainable (the first being the M40A3). The M21 has the lowest damage multipliers, but its low recoil and fast fire rate make it very easy to fire multiple rounds very quickly. This means that if the first shot is a miss, or does not kill the target, the shooter still has the opportunity to get the kill. Unfortunately, this can lead to the bad habit of trigger mashing, which can result in a lot of missed shots. It is more effective to aim and fire accurate shots individually, except for in a few situations, such as spraying through a wall or engaging a large number of targets at once. When fitted with an ACOG Scope, the M21 has almost no recoil, making it the most suitable sniper rifle for close quarters combat (however, for this purpose, it would be more practical to use the similar M14 rifle, or a weapon specialized for CQC, such as a submachine gun.)

Many consider the M21 to be the best sniper rifle in Hardcore modes due to its low recoil and the fact that all sniper rifles are one hit kills if a direct hit is landed. Statistically, the M21 and Dragunov are the best for Hardcore. The M21 has less recoil, and the Dragunov has slightly better wall penetration (if Deep Impact is on the difference is not noticeable and the M21 becomes the clear winner, unless one would want a slightly better hit multiplier in the chest). In most situations, regardless of perks, the M21 is more effective. In the computer version of Call of Duty 4: Modern Warfare, the M21 greatly increases sprint time if equipped as a primary weapon. This affects all snipers, despite some being heavier then assault rifles or even LMGs. Some maps where this gun is most effective are: Bloc, Countdown, Strike, and Overgrown because enemies are more visible and easier to tack.

Trivia

 * The M21 in Call of Duty 4 uses a Leupold MK4 10x scope, but it normally uses a Bausch & Lomb Tactical 10×40 scope.
 * This weapon is very similar to a M14 if equipped with an ACOG Scope but the M21 has more damage and less recoil.
 * Although the M21 sometimes appears in campaign with a suppressor and ghillie camouflage, it's unavailable like that in multiplayer.
 * The M21 is the only sniper rifle seen with a silencer.
 * The M21 shares ammo with the G3, M14, M40A3, and R700
 * If you turn the sensitivity to 10 and press and hold right, you can see the right side of the gun is not fully rendered.
 * The actual reload time and the reloading animation for a loaded reload are about 1.5 sec off, meaning you actually reload before the magazine is even inserted.

Video
thumb|left|300px|Gameplay with the M21