You will get much greater satisfaction if you abandon use of the aniquated characteristic called "Sectional Density", and use instead a measure that will correlate well with penetration - namely momentum. It is calculated as mass time velocity. (As opposed to kinetic energy which is of course one half the mass times the velocity squared.) Of course bullet design matters, but within a given bullet design, momentum is head-and-shoulders better as a predictor of penetration than sectional density is.

Paul