The Johnston Model D1918 was a light machine gun. It is a rare and little-known weapon with scant information available on it. It is best known for its resemblance to the Lewis Gun, having a similar gas-operated action and a barrel surrounded by a cooling shroud.The weapon was chambered for the .30-06 round, fed from double drum magazines.The action was gas-operated, with the piston working in a cylinder beneath and integral with the barrel.