I really don't see much point to the chainsaw handle. Awkward to aim, awkward to pump, can't imagine it's really any better as a door breacher than a standard PGO Mossberg, and then once you breach the door the standard shotgun will still atleast be a good CQB weapon.
It would be cool on a semi-automatic Saiga with a drum mag so you can atleast do some awesome looking hip-fire mag dumps. But on a pump-gun, you'd just look stupid.
The only saving grace is if you want a short, tactical Mossberg and this is the only thing in stock at the store, atleast you can buy it and take the handle off.