I also think that you must place your shot right. Last week i shot a doe at 10 yards with no passthrough and didnt get her. Then 2 days ago i shot a doe at 40 yards and it went through both shoulders, complete passthrough. Very amazing to go through both shoulders at 40 yards. I took pics for posts like this.
http://i15.photobucket.com/albums/a362/bowngun88/100_0072.jpg