My 13 yr old grandson shoots 100gr Swhacker heads from a 51 lb PSE bow. He shot a spike at about 20 yds in the shoulder this past Sunday evening. Arrow penetrated about 2" , the deer ran and the arrow fell out. He recovered the arrow and broad head and the arrow was broken right at the head. He killed anther spike that evening at 30 yds with a behind the shoulder shot - arrow past clean through. What went wrong with the first deer that was shot in the shoulder?