1867 Roper (U.S.) Cylinder Shotgun (repeating/ breech-loading/ black powder/ cartridge shot ammunition) Made at Amherst, Massachusetts in 1867, this arm uses four cartridges that fit into a revolving housing. Incredibly, all the basic movements of a 20th Century machine gun are present in this system. Its bolt, when moving to the rear, cocks the gun, withdraws a spent cartridge from the breech, and revolves the housing to bring a new cartridge into battery.
The now forward-moving bolt then injects the new cartridge into the breech, and the gun is ready for firing. True machine guns use propellant gasses to cycle the bolt.
Instead, the gas is vented, and the shooter’s thumb must provide the energy. Roper knew about all the physical forces that were available to operate a gun. Yet, he was not able to harness them for work.
John Browning would later accomplish this feat. –Dr. William L. Roberts, THE AMERICAN LIBERTY COLLECTION; #83 The design of the Roper revolving magazine shotgun overcomes a problem common to nearly all revolving firearms.