I have not had copper bullets not function properly but this one did not, but it had plenty penetration. the bullet went in just in front of the right eye,thought the neck,shattering the left shoulder and stopping in the skin half way down the left side and there was a hole in the rib cage some how one shot only in a 200 pound boar, with a 20 gauge shot gun at 800 yards just kidding it was about 35yards.