Being a tail gunner on a B-17 Flying Fortress was a lonely existence, much like the ball turret gunner. The gunner sat at the very tail end of the plane in a tight location always looking to the rear. In addition to being the gunner he was also the eyes for the rest of the crew and could give a heads up on approaching enemy aircraft.
The earlier model flying Fortress did not have a gun in the rear position and relied on the waist guns to cover the rear. At the time the waist guns were in a bubble and could be depressed further to the rear, but it became apparent that a dedicated rear gun was needed.
They first tried a powered turret but it did not work out, a real person would be needed to operate a gun. The first manually operated gun sat on a pin mount with cables running back to the gunner. The gunner had to maintain some kind of reference point with the sight in order to gain any accuracy.
A reference point was hard to maintain because of the bouncing of the aircraft.Later they came up with a reflector sight which freed the gunner from having to maintain a reference and increased the accuracy of the weapon. In addition to the gunners cramped position, it was a very cold position at 30,000 feet. There was a lot of air blowing through the compartment making for freezing conditions. The tail gunners eventually became good at their job and enemy pilots became reluctant to approach from the rear.
Flying Fortress Tail Gunner Position