AA-12
Fully automatic.
30 rounds
Can fire 30 mini-grenades.
Virtually no recoil.
https://www.youtube.com/watch?v=9DWUYQo4UGY
I believe that is what they were using in the first Expendables movie.
That was it! I recall a video where an average sized female was firing the 12 gauge full auto with no problem. Very impressive!