AA-12

The AA-12 (Atchisson Assault-12) is an automatic shotgun considered to be the first shotgun directly designed for military use. It is available in Call of Duty: Modern Warfare 2.

Call of Duty: Modern Warfare 2
The AA-12 is known to be capable of accepting the Red Dot Sight, Suppressor, Heartbeat Sensor (SP only), and Jacketed Ammunition (even though shotguns fire buckshot). It has an 8-round magazine capacity and 16 with the extended mags, balancing the weapons power and speed, but may have a capacity of 70 extra shells, and fires full-auto. The AA-12 empties its magazine far more quickly than it reloads as the magazine needs to fit onto the magazine support, and then slide up into the magazine well, though this is slightly offset when using the Sleight of Hand Perk. Since it uses magazines rather than individual shells, it is the fastest loading shotgun in the game. When using the AA-12, try firing it in bursts, and not to hold down the trigger unless completely surrounded in close quarters. In multiplayer, the AA-12 has only one extra magazine, so use it sparingly (unless you have Scavenger to keep your ammo count up.) It also has moderate recoil and little range compared to other shotguns, so players will have to get fairly close to use it effectively. Using Extended Mags increases the shotgun's magazine to 16 rounds, allowing the user to fire it for longer. This makes it a very good weapon for clearing rooms full of enemies. To many people's suggestions it has the worse range of all the shotguns, almost just having to be near point blank range to cause any harm, and its fire rate is so high you would have to manage some control with the weapon, so people wish an update issued for it to have more magazines, slightly lower fire rate, and slightly higher range.

Call of Duty: Modern Warfare: Mobilized
In game, the AA-12 is used in the U.S. Marine missions. It comes with a 32-round drum magazine by default, more damage and slightly slower automatic fire than the console version. It is the second last weapon to be unlocked for the USMC/SAS multiplayer faction.

Trivia

 * The AA-12 fires faster and has lower recoil in singleplayer than in multiplayer.
 * The AA-12 was developed in North Carolina.
 * In real life the AA-12 has roughly twice the range of other shotguns, and virtually no recoil. This is not the case in Modern Warfare 2, more than likely for balancing purposes.