ACR

The "ACR" (Adaptive Combat Rifle) is a contemporary multi-caliber assault rifle. It is a variant of the updated version of the Masada Adaptive Combat Weapon System, which was made by Magpul prior to their licensing agreement with Bushmaster (who makes the civilian version) and Remington (who produces the military version). The weapon borrows traits from other firearms, most notably the ambidextrous operating handle in a forward position, similar to the SCAR-H, as well as SCAR-style modular construction. Its internal components are heavily influenced by the AR-18, a piston-operated alternative to the AR-15 developed by Armalite. The ACR is intended to fire with 5.56x45mm NATO, 6.8mm SPC, 6.5mm Grendel, and 7.62x39mm ammunition. The ACR uses a quick-change barrel system that allows it to change calibers quickly, and it can use STANAG type magazines. The Remington ACR is unlocked at level 48 in multiplayer.

Modern Warfare 2 uses the 14.5-inch barrel configuration. The ACR is only used by TF141 and Shadow Company. It is also commonly used by Ghost and Roach, and is their starting weapon in most TF141 missions in the game.

Call of Duty: Modern Warfare 2
The ACR is first used in the mission Cliffhanger, with a Red Dot Sight, Silencer and Heartbeat Sensor attached (this is impossible in multiplayer because there is a maximum of two attachments per gun), although it is also present in the first mission S.S.D.D. as one choices of weapons for running the Pit, located inside one of the weapon crates with an EOTech Holographic Weapon Sight attached. The design of the ACR in Modern Warfare 2 bears heavy resemblance to the original Masada Rifle design by Magpul (one difference is the charging handle, it has the ACR's charging handle not the Masada's) rather than the actual ACR manufactured by Remington.

Multiplayer
In multiplayer, the weapon is unlocked at Level 48. It carries 30 rounds in its magazine, deals 20-30 damage per shot, and has a fire rate of 750 RPM. The ACR, although it bounces when firing, has zero recoil as it resets perfectly before the next shot which makes it ideal for medium and long range combat. Its moderately low damage per second makes it somewhat weak in close quarters combat compared to other automatic weapons, making it a good candidate for use with the Masterkey Shotgun and/or Stopping Power.

As a versatile weapon, most Perks and Attachments work well with the ACR, allowing it to fill a variety of roles. The ACR is primarily used at long ranges and excels in medium- large sized and large maps with long sight lines such as Wasteland, Afghan, Highrise and Derail. Unlike most weapons, the ACR suffers no noticeable increase in recoil or sway from the use of ACOG. The ACR consumes ammo fairly quickly, but its complete lack of recoil means that wasting ammo due to missed shots is usually not an issue.

In terms of damage output per second, the ACR's low damage and moderate rate of fire make it one of the lowest damage output weapons in the game. The ACR makes up for this at medium and long range with its perfect accuracy while still firing fully automatically. This makes it kill quicker than weapons with more recoil, which force the user to burst fire to maintain accuracy at medium to long range.

Weapon Attachments

 * Grenade Launcher
 * Shotgun
 * Red Dot Sight
 * EOTech Holographic Weapon Sight
 * Silencer
 * Heartbeat Sensor
 * ACOG Scope
 * Thermal Scope
 * FMJ
 * Extended Mags

Trivia

 * On the side of the weapon it says "Maneemagusswa Mamdaero, Cal 5.56 Euro"
 * On Infinity Ward's website, the ACR was voted the favorite assault rifle in Modern Warfare 2.
 * Modern Warfare 2 is the first video game to feature the Remington ACR as a usable weapon.
 * In Just Like Old Times there are three ACRs that are in the same configuration as the ACR from Cliffhanger, possessing Red Dot Sights, Silencers, and Heartbeat Sensors. Both of these ACRs have unique camouflages, with the one from Cliffhanger using a variant of Arctic camo while the ones in Just Like Old Times are completely black. The ones from Just Like Old Times also have a maximum ammo count of 1260 rounds.
 * In Just Like Old Times players can have two ACRs with Holographic Sight or an ACOG Scope at the same time, with the only difference being their camo patterns.
 * Many of the ACR's controls such as the charging handle, fire controls, safety and mag release are ambidextrous, unlike the M4 which it was designed to replace, which has controls only meant for right-handed people.
 * The ACR appears to be the signature weapon of Shadow Company. While they wield a variety of weapons, the ACR is very common, and vast quantities of them in every imaginable configuration are found at Site Hotel Bravo.
 * The ACR appears larger than any assault rifle when seen from 3rd Person.
 * Although a Bolt Catch is present on the ACR, the in-game reload animation still shows the charging handle being used as a way to load a new round to the gun's chamber.
 * Heartbeat Sensors appear much smaller in this gun than any other assault rifles.
 * Like the UMP .45, the Iron sight is removed with the addition of the Red Dot sight.
 * The serial number of the ACR in Modern Warfare 2 is 0091436.

Video
thumb|400px|left|ACR gameplay