The deer I took this year at 20 yards with a 30.06 left no blood trail whatsoever even though the exit wound was in the brisket, with the heart blown out. The deer went 60 yards and the entire body cavity was flooded with blood but no blood trail. Deer was seen drooping in its tracks but trailed it from point of impact anyway to gain practice in blood trailing. . Tracked it easily enough by hoof impressions but no blood to be found...anywhere except 10 feet from where it lay dead/.....1 drop on a leaf. Don't rely on blood to indicate mortality or a hit. Look at the big picture.