In multiplayer, the Adaptive Combat Rifle is unlocked at Level 48. The ACR is similar to the M4A1 but sacrifices rate of fire for higher accuracy and has virtually no recoil. It carries 30 rounds in its magazine, deals 30-20 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.
As a versatile weapon, most Perks and Attachments work well with the ACR, especially Stopping power which allows 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 lines of sight such as Wasteland, Afghan, Highrise, Derail, Estate, Bailout, and Fuel. 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. Moreover, it should be noted that the ACR is one of the most effective weapons in the game for reload canceling; the player doesn't even need to wait until the magazine is fully inserted into the rifle before ammo is replenished.
Getting headshots with this gun is much different than getting headshots with other guns. With the ACR you must actually aim at the head whereas with other guns such as the UMP45 which has vertical recoil which make it easier to get headshots.
In terms of damage output per second, the ACR's low damage and moderate rate of fire make it one of the weakest weapons in the game, with almost every other gun outperforming it, in close quarters especially. However, it more than makes up for this at range, where its non-existent recoil ensures all shots go on target, which effectively makes it kill quicker than guns where burst-firing is necessary.