Its been called the greatest automatic rifle of all time—the John Moses Browning-designed Model 1918 Browning Automatic Rifle. Browning actually created gas-operated self-loading firearms. Noticing the disturbance in the grass caused by the passing of a bullet out of the muzzle, Browning hooked a “flapper” onto the barrel of a lever-action that harnessed the expanding propellant gasses through a hole drilled in the barrel. He used the force of the gas to move a lever linked to the action to cycle it. That principal, what we call gas-operation, was applied to the Colt Machine Gun Browning designed in 1889, better known as the Model 1895, and later the Model 1914 called the “Potato Digger” before eventually becoming the Browning Automatic Rifle.
Watch this episode of American Rifleman TV's "I Have This Old Gun" to learn the full history and see the gun in use.