History

The Auto Assault-12 (AA-12), originally designed and known as the Atchisson Assault Shotgun, is a shotgun developed in 1972 by Maxwell Atchisson. The current 2005 version has been developed over 18 years since the patent was sold to Military Police Systems, Inc. The original design was the basis of several later weapons, including the USAS-12 combat shotgun. The weapon is selective fire, operating as a semi-automatic, or in fully automatic mode at 300 rounds per minute. It is fed from either an 8-shell box magazine, or a 20- or 32-shell drum magazine.

In 1987, Max Atchisson sold the rights of AA-12 to Jerry Baber of Military Police Systems, Inc., Piney Flats, Tennessee. MPS in turn developed the successor simply known as Auto Assault-12, which was redesigned over a period of 18 years with 188 changes and improvements to the original blueprint. MPS also teamed up with Action Manufacturing Company, and Special Cartridge Company to combine the gun with FRAG-12 High-Explosive ammunition into a multifunction weapon system.
 
The weapon was lightened to 4.76 kg and shortened to 966 mm but retained the same barrel length. The CQB model has a 13-inch barrel, and is half a pound lighter than the regular model. Uncommon in other automatic shotguns, the AA-12 fires from an open bolt, a feature more commonly found in submachine guns and heavy and squad level machine guns. It uses 8-round box, 20-round drum, or 32-round drum magazines, as opposed to the original 5-round box magazine. Due to the abundant use of stainless steel and the designed clearance for fouling, MPS has claimed that the weapon requires zero cleaning or lubrication.[3] The designer states that cleaning is required after 10,000 rounds.

The AA-12 can use different types of 3" 12 gauge ammunition such as buckshot, slugs, or less-than-lethal rubber stun batons. It can also fire flares or special Frag-12 19 mm fin-stabilized HE, HEAP, and sensor fused HEAB "air-burst" fragmentation shells that can detonate in mid-air.
 

 
In 2004, ten firing models of the AA-12 were produced and demonstrated to the United States Marine Corps.
 
The HAMMER unmanned defense system by More Industries uses dual-mounted AA-12s on the H2X-40 Turret. Neural Robotics has also mounted the weapon on their AutoCopter Unmanned aerial vehicle.

Singleplayer/Spec-Ops

Multiplayer

The AA-12 has been reduced in power from Modern Warfare 2 in several ways. First, the spread is much wider, necessitating Steady Aim. Second, the Damage has been reduced from a 20 to 15, making the Damage proficiency very attractive (as with all shotguns). Third, the Extended Mags attachment has been reduced from 16 to 12, bringing it in line with the 50% bonus all other weapons receive. Scavenger is practically a necessity for the AA-12, as the starting ammunition is the lowest of any shotgun and the rate of fire is the highest. With all of the aforementioned perks and attachments, the AA-12 plays almost identically to the Modern Warfare 2 version, capable of clearing out large rooms with ease, but having the most limited range of a shotgun.

Attachments

Attachments	Challenges	Icon
Grip	Get 20 kills with a Grip attached to a Shotgun.
Silencer	Get 15 kills with a Silencer attached to a Shotgun.
Reflex Sight	Get 60 kills while looking through a Red Dot Sight attached to a Shotgun.
Holographic Sight	Get 40 kills while looking through a Holographic Sight attached to a Shotgun.
Extended Mags	Get 40 kills with Extended Mags attached to a Shotgun.

Proficiencies

Proficiency	Description	Icon
Kick	Kick Reduces recoil by 20%, allowing for steadier full-auto and faster recovery from shots.
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.
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.
Melee	Grants 35% faster melee recovery. Melee can be useful if you are stalking targets with a stealth Shotgun build. With the Riot Shield, it allows you to take down targets much more quickly at close range.
Range	Offers a 25% boosted effective range. This is very useful on Shotguns, particularly the automatic variants. Some SMGs can benefit from this upgrade, as well, especially if you are intent on using medium-range optics.
Damage	Provides a significant 40% Damage boost. Damage is strong on the Shotguns that already have solid range, and very important for pump-action Shotguns that may not get a second shot.

Challenges