The Cobray Terminator shotgun is a very odd invention.
This 12 gauge single shot shotgun is rare with only about 1500 ever made. This single shot shotgun worked on an odd system unlike any other of its kind.
How it works: the barrel is under spring pressure, and when the trigger is pulled the barrel slams backwards toward the shooter into the fixed firing pin.
A simple design, but more useful in open bolt machine guns than in a single shot shotgun. Lack of sales killed this weird shotgun early in its life.
This interesting failure is just one of many in the history of firearms development.