The Sperry ball turret, meant for ventral defense needs on aircraft, was used on both the B-17 Flying Fortress and the B-24 Liberator as well as the United States Navy's Liberator, the PB4Y. The Sperry ball turret was very small in order to reduce drag, and was typically operated by the shortest man of the crew. To enter the turret, the turret was moved until the guns were pointed straight down. The gunner placed his feet in the heel rests and then crouched down into a fetal position. He would then put on a safety strap, close and lock the turret door. The gunner sat in the turret with his back and head against the rear wall, his hips at the bottom, and his legs held in mid-air by two footrests on the front wall. This left him positioned with his eyes roughly level with the pair of Browning M2 .50 caliber machine guns which extended through the entire turret, and located to either side of the gunner. The cocking handles were located too close to the gunner to be operated easily, so a cable was attached to the handle through pulleys to a handle near the front of the turret. Small ammo boxes rested on the top of the turret and the remaining ammo belts were stowed in the already cramped turret by means of an elaborate feed chute system. A reflector sight was hung from the top of the turret, positioned roughly between the gunners feet. - Wikipedia