castaway,is it possible you nicked a branch on the way to the armored deer? Reason I ask ,I had a similar experience with a 30-30 and 180 grain bullets.My brother said he saw "some thing" before the bullet hit the deer.The entry wound was a profile or key hole .We found the slug deformed and in the on side rib cage.The heart and lungs and liver were damaged.When We told my grand pop about it he took us back and found a branch that was nearly sheared off between the shot and deer.I did hit it a few inches back,but never saw the branch.