a true double lung shot is a shot that hits both lungs. And a deer can be shot in both lungs and live for a long time. It does not have to be a square in the middle of thge lung. The deer I had the experience with was shot low and towards the back of the lung. but it was through both lungs. It was a "double lung" shot. And the deer lived from 8 in the evening till a little after six in the morning. it was crazy. So much blood loss. But when we came up and found himn he was still breathing. Laid all the way down and didnt even raise his head when we came up. We put another arrow through and killed him then gutted him. I have pictures at home I will post tonight if I find them