This is a very unique weapon, it has a combination of power, range and magazine size, in the hands of an exprienced user, it can cause death and destruction, mincing up enemies.It looks like a fictional gun but close inspection reveals that it may be an Armsel Striker Shotgun that has been heavilly modified, more evidence to support that claim is that it has a 12 round drum mag and it is semi-automatic.
It is one of two semi-automatic shotguns, the other being the S.P.A.S 12.
Reference[]
gamingupdate.com