The AA-12 is a unique shotgun because it's fully automatic. It has an 8-round magazine capacity, which is doubled when Extended Magazines is attached, which balances the weapon's 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 (650 RPM singleplayer) 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. TIP: When using the AA-12, try firing it in bursts, and not to hold down the trigger unless completely surrounded in close quarters. Firing full automatic introduces significant vertical recoil, even with the grip.

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 poor 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. Many people have suggested it has the worst range of all the shotguns, having to be near point blank range to cause any harm, and its fire rate is so high you have to keep some control when firing the weapon. It is recommended that a user uses Scavenger with the AA-12, as its ammo runs out after two magazines, or one if the player is using Extended Mags.