As you can see, he fired the first 6 rounds to no effect. This is not unusual, as most RAF personnel can't hit the target anyway!
He then reloaded a further 6 rounds. Round #7 joined the others in the barrel, and #8 then went '
bang' ... but could not go far enough to allow the cylinder to continue to rotate, so the pistol was completely jammed up. At this point proceedings were halted