The Mossberg 590 Shockwave is that company’s version of the legendary “witness protection” shotguns originally developed for the U.S. Marshall’s Service. These cut-down shotguns were prized for how easy they could be concealed under a coat or windbreaker and for their quick handling.
One advantage of the Mossberg product is that since they are factory built on virgin receivers they are classified as “firearms” and not “Short Barreled Shotguns” or even “Any Other Weapons.” This means they are transferred as regular Title 1 firearms and do not require any additional taxes or special permits under Federal law. (State laws may vary.)
In the video a Mossberg rep goes over the feature set of the Mossberg Shockwave.