History

The Colt CM901 is a modular firearms platform that can be converted from an assault rifle to a battle rifle as well as carbine length barrels without the use of tools .
 

 
The CM901 (Colt Modular) weapons system is based on Colt's existing M16/M4 military designs. It shares the direct gas impingement operation, as well as much of the action, controls, and basic aesthetics with previous Colt rifle designs. The system's heart is a common lower receiver housing an enlarged magazine well that will accommodate larger caliber ammunition than NATO 5.56x45mm rounds, ambidextrous controls for the bolt release mechanism, magazine release, and fire selector/safety lever, trigger group, pistol grip, telescopic stock, and buffer tube. The system will accept a series of upper receiver assemblies that contain the respective action required to accommodate the various caliber rounds accepted by the weapon. A re-designed upper receiver firing standard 5.56mm ammunition will be produced in various barrel lengths, all having a monolithic design with a full-length top rail, and three auxiliary rails for mounting accessories, free-floating barrels, and front and rear flip-up sights standard, when not using upgraded optics.
 
Upper receivers will be available in several calibers and barrel lengths, as small as 10.6" for the 5.56mm model. The lower receiver will also accept older mil-spec M16 or M4 upper receivers without an adapter. Receivers will be available that accept 5.56x45mm NATO rounds, 6.8x43mm Remington SPC rounds, 7.62x39mm rounds, and 7.62x51mm NATO rounds. Each upper receiver has its own rail system, which allows scopes, or other optics to be pre-sighted for each configuration, and swapped quickly to perform different tasks.
 
The system can be anodized in a standard matte black finish, but has standard color options including Desert Brown, Digital Camouflage, and Vista Camouflage, which are applied during the anodizing process to prevent wear during use.
 

 
At its unveiling, Colt planned to release several variants of the CM901 system over the course of 2011, with the civilian "SP901" being the first, in Q2 to Q3 2011. The civilian model will be available with all the same features and finishes as the planned Law Enforcement and Military models, but will ship stock with a semi-automatic lower receiver, and an upper receiver with a 16" barrel chambered for .308 Winchester ammunition. This variant will also accept civilian AR-15 upper receivers of multiple barrel lengths, and includes a magazine well adapter to accommodate smaller STANAG magazines.

Singleplayer/Spec-Ops

The CM901 is an Assault Rifle that appears in Call of Duty: Modern Warfare 3. It is seen in Spec Ops and the Call of Duty XP multiplayer reveal. 

Multiplayer

TheCM901 is unlocked at level 18 in multiplayer. The CM901 is a versatile assault rifle due to its moderate-high damage, very clear iron sights, and controllable recoil due to the low fire rate. This fire rate can be disadvantageous in close-quarters, however, as it is the slowest full-auto assault rifle and the third slowest automatic weapon in the game. As such, players using this weapon should pick their engagements wisely.

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