Rick,
We went through some of this a couple of years ago, as I recall.
The straight penetration of solids also depends on frontal shape. Spitzers are worst, but round-nose solids aren't great either, especially if marginally stabilized. Flat-nosed solids (such FP handgun bullets) result in more damage due to a physical phenomenon called cavitation. I am not about to repeat the reasons for all this, since it's explained thoroughly in Chapter 3 of Gun Gack II.
