Waist gunners had the distinction of manning the position with the most casualties. It was the least well protected and frostbite was a major concern. Unlike the nose, ball and tail turrets, which dumped spent .50 caliber shells through shoots in the floor, the floor of the waist positions filled with spent shells during attacks. The gunners sometimes used a shovel to clear a place to stand. The first waist guns used simple open sights, but compensating sights were developed which took into account air speed and relative speed of target.