Wow. 55 missions as a rear gunner??? You use us a lot of luck doing that just once. May you fly with the angels once again.
This is more amazing considering that RAF Lancasters used 0.303 caliber machine guns for their turrets, which had a lot less hitting power than the 0.5 caliber machine guns used on American bombers.
*And* he made ace to boot - despite the fact that he wasn’t flying the plane.