You have to get the idea out your head that ballistic gel has any direct correlation to how a bullet will perform in human or animal tissue
or that it is meant to do that. All the various complaints about "well it doesn't show bone"or "it doesn't account for different densities of body organs", etc. are true and also meaningless. Meaningless because they miss the point entirely.
The significance of ballistic gel is that it allows manufacturers and labs to design bullets that will meet certain criteria and provided a uniform testing media for that performance that roughly approximates the density of mammalian body organs.
Nothing, not gel, not computer models, not testing on live animals, not studying autopsy reports, not after action reports from cops, can predict how a bullet will perform in the real world. In fact extensive testing by the U.S. Army has validated just this point. Each bullet fired is it's own experience. Testing can only provide a rough idea of how certain bullets can perform. Gel testing provides an uniform method of doing that and transferring the results.
Once a bullet has been built that penetrates windshield glass, 3 layers of denim and penetrates 12" in ballistic gelatin and does this reliably, repeatedly in testing then it's likely that it has the capability to do so in the real world more reliably than a bullet that can't do it in the lab. It doesn't mean that it will neither is the point of it to try to guarantee that it will.
Below are two charts comparing two separate loadings of the Speer GDHP from the Federal website. Both feature two 40 S&W 165 gr. loads. 53970 moving at 1150 fps from the muzle and 53949 traveling at 1050 fps. Both from a 4" barrel. The tests show the results from both bare gelatin and after penetrating various barriers and into gelatin.
http://le.atk.com/ammunition/speer/handgun/compare.aspx?compare=53949,53970
http://le.atk.com/downloads/technical_bulletins/PenetrationComparison53949vs53970.pdf
The results can help a person in bullet selection to fit their situation and need but they are no promise. They are not intended to be.
Some may think this is bad news. It isn't at all. The results have been a great step forward and enabled the construction and uniform testing of a wide range of effective bullets which operate more consistently than those of the past.
tipoc