Many scholarly studies have shown that, for the most part, properly chilled ballistic gelatin simulates average penetration in tissue. Obviously, softer tissue (lungs, abdomen) will have more penetration while denser tissue (muscle) will exhibit less. For the most part, however, gelatin testing is a good indicator of how a round will perform on average in tissue. Built into the expectations for a successful gel test are margins for performance. 12" of penetration as an expectation (the FBI standard) is intended to cover the vast majority of shooting situations. While every ballistic encounter is unique, rounds that perform consistently well in properly prepared and calibrated gelatin can be expected to perform similarly well in actual tissue.
Often we see makers, backyard experts and others shooting things like a rib roast, a slab of beef or other strange food items (our favorite is fruit) and attempting to compare these results to results in human tissue. We also see people comparing deer results with results they expect in humans. "I killed a dozen deer with it... it must be a man stopper."
This is, unfortunately, folly. Deer, to begin with, have SUBSTANTIALLY different anatomies than humans (surprise surprise). The distance in tissue to vital organs is different, bone density is different, the location and strength of CNS structures is different, as is the vascular system. Further, because the CNS structures of deer are somewhat more primitive and less intricate than those of humans, they are far less fragile in some places, far more fragile in others. What works in deer may or may not work in humans. The same goes for hogs, varmints, pigs, dogs, zombies (headshots only please), and aliens (particularly grey skins- go for the big eyes, not center mass).
Likewise shooting a side of beef isn't good for much but making hamburger.
Why gel? Gel can be made consistent. We can compare apples to apples with gel and see that one round performs in it better than another. It is transparent and so we can measure ACTUAL wound cavities rather than just a gaping exit hole. Fragments are left behind in gel much as in tissue so we can measure fragmentation, and finally, properly calibrated gel has been linked by at least six studies to performance in human tissue. This bears repeating because many people choose to ignore this. Performance in properly calibrated gel simulates very closely performance in human tissue in test after test.
The trick with gel is asking "was the gel properly prepared and shot?"
When looking at test information focus on several factors: