At one of these air shows with a B-17, I met a former ball turret gunner as we toured the inside of the plane.
In his seventies, still thin and wiry and short, he said he was picked for the ball turret because of his size. He said that there was no room to wear the parachute so he kept it outside the ball, next to it on the floor of the plane. The ring gear held the ball into the plane, and allowed the rotation of the ball in all directions. The entry door in the plane had to be aligned with the entry door in the ball in order to acces and leave the ball.
If flak damaged the ring gear, you could be stuck in the ball until you landed. Same thing if the plane was going down and you could not align the doors to get out, you were done.
And if the flak blew out the ring gear, the ball would detach from the plane with you in it—and no parachute. That was back in the plane.
He was 19. He survived 30-something missions. To him, it was just his job. To me, it was amazing how brave my fellow Americans can be.