First off NFA rules dictate full auto ANYTHING would have have a DoM of previous to the 1986 ruling.
Secondly, the AA-12 is a Destructive device by definition...
Bore in excess of .50 inch.
Smooth bore breech loading shell firing.
i think both apply and there may be other factors...
If you want the real truthful skinny on any such considerations, I refer you to the "NFA" section below this one... Them folks got the dope on the whole NFA realm.