Originally Posted by Nanuk:
Then how do you leap from testing in water, or gelatine to arrive at an accurate indicator of performance and effectiveness?
There is no such "leap" to be made.
Testing in such mediums (gelatin, water) yields measurable, recordable, repeatable data (not anecdotal heresay) such as average expansion, penetration depth, and amount of tissue damaged in the wound track which are
indicators of performance and effectiveness.
After that, what that particular bullet design hits is what matters and that cannot be predicted.