Most don't know that the AA12 has actually been around for a long time (first one was in 1972), first as the Atchisson Assault Shotgun which gave us the USAS12 (a more M16 looking auto shotgun) and now we have the Auto-Assault 12 which was developed for today's soldiers. Using Stainless steal and allowing for fouling clearances it was designed to not need cleaning or lubrication until 10,000 rounds and can take some serious pounding and muck.
The new designers did a lot of thinking to make sure that the AA12 can be used in various roles including launching small 12gauge frag grenades that were developed alongside the AA12. It was also designed to be used on UAVs as well. There are several unique characteristics of the AA12. One of those is that the AA12, unlike many assault rifles, fires from an open bolt design that allows for some absorption of the recoil which makes the AA12 very easy to shot as the large amount of recoil that would be generated in full auto mode would be uncontrollable otherwise. Unlike the first AA12 the new one has an 8-round box magazine and optional 20 and 32 round drum magazine. With the Polymer stock and stainless steal internals it's not hard to add accessory rails which allows for adding of tactical and optical accessories as well.
I haven't maxed out the AA12 in MW2 so I don't know if you get the drum magazine when you get the extended mag unlocked but hey it's a fun shotgun until you unlock the better duel welding ones later in the game and I wouldn't mind finding an AA12 that someone would let me shot as I think it would be fun to test and you know several years ago I did actually see a USAS12 semi-auto at Impact Guns here in Boise that was for sell. They only wanted $700 at the time.
Here's a video of the AA12 in testing. You can find the Future weapon clip of it on YouTube as well.
