History

The Steyr ACR was a prototype flechette-firing assault rifle built for the US Army's Advanced Combat Rifle program of 1989/90. Although the Steyr design proved effective, as did most of the weapons submitted, the entire ACR program ended with none of the entrants achieving performance 100% better than the M16A2, the baseline for a successful ACR weapon.

The Steyr ACR has some superficial resemblance to the Steyr AUG, although it is rounder and the barrel is covered for almost its entire length, as opposed to the AUG where much of the barrel was exposed. Like the AUG the ACR is a bullpup design with the 24-round magazine located quite close to the buttstock of the gun. The stock was "split" from the magazine forward to a location just below the sights to open for cleaning. An optical sight was included as a standard feature.
 
The Steyr employed a unique system to cycle through ammunition: instead of driving rounds forward into the chamber and being held in place by a locking bolt, the entire chamber traveled vertically the width of the round. After firing the gases "blew" the chamber vertically downward where a new round was forced into the chamber from the rear, forcing the old round out an ejection port ahead of the magazine. Springs then raised the chamber back into position where it was locked into a fixed block. The firing pin was fixed above the chamber, entering through a small hole and striking the ring of primer to fire. The chamber was normally held in the "down" position, the trigger releasing it to allow the springs to drive it upward and fire.
 

 
The Steyr ACR's rounds consist of a carbon steel flechette for a projectile that used a four part spindle sabot packaged in a telescoped arrangement with propellant packed around the projectile. The case of the ammunition was made of a light weight translucent plastic instead of conventional brass making the rounds weigh less than half the weight of standard 5.56x45mm NATO ammunition.
 

 
During testing the weapon performed well, and only two problems were identified. One was that the plastic cases had varying strengths, which has some effect on the ballistics. This was considered to be a fairly minor problem, one they expected could be solved through better materials and quality control. The other issue was somewhat more difficult to solve; when the sabots left the barrel they were still going quite fast, and presented a danger to other soldiers as well as to the shooter if they bounced off the ground when firing prone.

Singleplayer/Spec-Ops

The ACR is seen in Scorched Earth with a Hybrid Sight.

Multiplayer

The ACR 6.8 is unlocked at Level 50 in Modern Warfare 3's multiplayer. It has the lowest recoil of all assault rifles, as well as having a good rate of fire and medium damage. Combined with fast reload, these stats can make the ACR work in every situation.

Attachments

Attachments	Challenges	Icon
Reflex Sight	Get 60 kills while looking through a Red Dot Sight attached to a Assault Rifle.
Silencer	Get 15 kills with a Silencer attached to a Assault Rifle.
Grenade Launcher	Get 20 kills with a Grenade Launcher attached to a Assault Rifle.
ACOG Scope	Get 20 kills while looking through a ACOG Scope attached to a Assault Rifle.
Heartbeat Sensor	Get 40 kills with a Heartbeat Sensor attached to a Assault Rifle.
Hybrid Sights	Get 40 kills with a Hybrid Sights attached to a Assault Rifle.
Shotgun	Get 40 kills with a Shotgun attached to a Assault Rifle.
Holographic Sight	Get 40 kills while looking through a Holographic Sight attached to a Assault Rifle.
Extended Mags	Get 40 kills with Extended Mags attached to a Assault Rifle.
Thermal	Get 40 kills while looking through a Thermal attached to a Assault Rifle.

Proficiencies

Proficiency	Description	Icon
Kick	Kick Reduces recoil by 20%, allowing for steadier full-auto and faster recovery from shots.
Impact	Impact grants maximized penetration for any weapon. This is especially powerful on Assault Rifles and SMGs, as LMGs already have strong penetration, and Sniper Rifles are difficult to use for intentional walling shots.
Attachment	Allows the use of 2 Attachments. It is a solid all-around Proficiency, useful in many situations. This Proficiency is also notably useful for stealth builds, as it allows you to use a Silencer alongside any other Attachment. The Attachment Proficiency is also helpful if you are still getting comfortable with iron sights, as it allows you to take and optical Attachment and a second utility Attachment.
Focus	Reduces visual recoil by 50% when you are hit. Focus is very effective for SMGs and Shotguns. It is also helpful for ARs, as it can keep your shots on target when you enter a heads-up one-on-one firefight.
Breath	Allows you to remove the slight sway from Assault Rifles by holding your breath. Very situational, most useful with the Type 95, M16A4 or MK14 with a long-range sight fitted. Breath can be used with automatics, as well, for careful long-range burst-fired shots, though the benefit is small.
Stability	Reduces idle sway by 25%. Consider this to be an 'automatic' Breath for long-range combat. It is most useful on LMGs, as they need the enhanced accuracy for long-range shots, though ARs also benefit from it.

Challenges