In the early 1960s, an influential but little-known (today) firearms designer by the name of Robert Hillberg came up with an idea for a cheap-but-effective armament for the masses. With encouragement from DARPA, the Winchester company took up manufacture and development of the design, under the name "Liberator".
The guns were initially planned to be made almost entirely as magnesium castings, with steel liners in the barrels, with a total cost of about $20 per gun. They would use prepackaged 4-round ammunition packets as well, rather than standard individual shotgun shells. By the time production was actually begun, however, the design had been altered to a break-action system using regular shells - the prepackaged quad-cartridges proved too difficult to perfect. So the production Mark II guns used conventional shells with a break-open action.
As it turned out, casting the frames over the steel barrel inserts was a quite difficult process, and Winchester soon moved to a MkIII design which replace the barrel casting with 4 independent all-steel barrels fixed at the muzzles by a stamped plate. By this time, however, military interest in the guns had fallen away and Winchester was left to try to market them commercially. They attempted to interest both police and civilian markets (although with 13 inch barrels, the guns were regulated by the NFA). None of these marketing attempts succeeded, and major production never began. The design was too impractical and guerrilla-oriented to really appeal to anyone with a more ordinary use (like recreational shooting, sport shooting, or security/law enforcement) in mind.
Thanks to the Cody Firearms Museum for allowing me access to film these! Check them out at: https://centerofthewest.org/explore/firearms/
USAS-12 Combat Shotgun: https://www.full30.com/video/957aac0957ae486f53ed7bbc248ef18c
Pancor Jackhammer: https://www.full30.com/video/05172f0bde59d073137b3185af684664
High Standard 10B Bullpup Shotgun: https://www.full30.com/video/5790be65e9d2024cf33243ea9225b62b
Burgess Folding Shotgun: https://www.full30.com/video/6d25dab3d714572890b5e87975fdc6b2
Cobray Terminator: https://www.full30.com/video/4e152ea1b63527a1d43b78a840813493