The B-17E was the first mass-produced B-17 model and literally bristled with armament. It was several tons heavier than the Model 299 prototype and included .50 caliber machine guns in a two-gun power turret on top of the fuselage just behind the pilot's cabin; a two-gun, maunally operated Stinger turret in the tail; and a power turret on the bottom of the fuselage behind the wing. A .30 caliber-gun remained in the nose, and two .50 caliber guns were on each side.