Ball turret A ball turret was a particular form of spherical - form , altazimuth mount movement manned aircraft gun turret , accommodating the gunner with nearly all the needed equipment for defensive firepower ( except for the ammunition storage ) mounted either within or onto the spherical shell of the turret structure , mounted on aircraft during World War II . The most common one was manufactured by the Sperry Corporation . Sperry ball turret . 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 light - barrel Browning AN / 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 gunner ' s feet . The turret was directed by two hand control grips with firing buttons similar to a one - button joy stick . Hydraulics normally powered elevation and azimuth . Hand cranks were available for backup . The left foot was used to control the reflector sight range reticle . The right foot operated a push - to - talk intercom switch . On the B - 17 the turret was close to the ground , but had enough clearance for takeoff and landing . However , the gunner did not enter the turret until well into the air , in case of landing gear failure . In the case of the B - 24 the Liberator ' s tricycle landing gear design required that the turret mount be made upwardly retractable into the lower fuselage while the aircraft was on the ground , since with the ball turret deployed for operation , the shell of the turret would be too close to the ground . For both aircraft types , there was no room inside for a parachute , which was left in the cabin above the turret . A few gunners wore a chest parachute . Erco ball turret . The Erco ball turret was the bow installation in the Navy ' s Consolidated PB4Y - 1 Liberator and PB4Y - 2 Privateer airplanes . It served a double purpose , taking care of any bow attacks on the Liberator as well as being used for strafing in anti - submarine warfare . Since this turret is of the ball type , the gunner moves with his guns and sight in elevation and azimuth as he moves his control handles . It is a relative of the Martin 250SH bow turret of the PBM - 3 twin - engined patrol flying boat and has many points of similarity in design and action .