15 feet. I was leaning against a tree and saw the deer to my left, about 40 yards away or so, I started to raise the gun to my shoulder and something spooked the deer. It ran towards me and I shouldered the rifle with just enough time to put one through it's lungs and heart as it ran past me and turned away. It was the absolute single most amazing shot I have ever made, and I could not do it again if my life depended on it. Usually my reaction to a running deer, is to stand and watch with a blank stare.