Hey J V,
Penetration is a very interesting subject. Weight retention has a pretty big role in it, but not nearly as much as I ever thought. We have seen through impact testing that a bullet that sheds some weight will out penetrate a heavier bullet that sheds no weight. It comes down to stability. After impact all bullets start losing their rotational vel rapidly. Pretty much every bullet will upset from its path once the rotational vel slows enough to cause the retained portion to yaw or even tumble. So even though a bullet has more retained energy and momentum there is a probable chance that a shorter retained shank of less weight will actually out penetrate because it will remain point on longer keeping it in straight line penetration longer. As soon as a bullet loses stability and turns it then is no longer traveling nose forward and catches much more surface area and slows down and stops more rapidly.
Our Hammer Hunter bullets are 60% to 70% weight retention, for the most part, depending on nose length and the Shock Hammers are 75% to 85% Weight retention.