I don't wish to get to deep into physics and am not a mathematician but my personal feeling is that "stopping power" is an assessment of Mechanical Work .Specifically, it is the application of energy to a to perform Positive Work,( energy transferred by a forcethru a distance . ie-The animal shot performs Negative Work to slow the bullet down.

Work= energy transferred by a vectored force thru a distance . Force has a direct association with momentum

This work is perfomed over a distance ie the bullet path.The 3d cylinder of work can be short and fat or long and thin if the bullet shoots right thru the animal and the animal offers little resistance to the force("cone of work").

Greater "stopping power" would seem to equate to a large diameter bullet with adequate depth of penetration.ie A short fat "cone of work" with adequate depth(length).

Given a constant resistance suggesting a consistent reproducible ability to stop the "work" of the bullet tables of "stopping power" should be able to be calculated--

again, If I am basically wrong someone please correct me-