Stopping power is not the question; caliber is not the answer.
[I have no LEO or military experience. I am considering the question from the POV of considering what's the most reliable and accurate way to answer the question given the data we have available. Considered from that POV, the question becomes mainly a question of data verification, research protocol, and the proper use of statistics.]
It has been pretty well established by military and police investigators and actual experience that semi-auto's are better tools for combat and self defense (as long has the shooter has been well trained in its use and has sufficient practice) than revolvers except for a few specialized situations. You may prefer a revolver for various reasons, and it is true that a revolver can be an effective tool in most situations.
There is no reliable, accurate, scientific, statistically valid data available which will enable us to compare the "stopping power" of one load to another. There is no data (and probably never will be) which will enable you to make predictions about stopping power involving a particular bad guy in a particular situation.
A more sensible question would be based on comparing specific loads, not "calibers". Consult the gelatin tests using the FBI testing protocols with and without barriers which you think you are likely to encounter. The following question is more useful and is the best we can do with the available knowledge: Which specific loads which can be accurately and swiftly fired by the shooter have the potential to cause the most damage (after penetrating likely barriers) to a bad guy without increasing the risk to bystanders?
When you look at the test results, you will find several loads which are similar in performance. If two loads do not vary more than 1" in penetration or .1" in diameter of expansion, consider them equivalent.
Since we can't measure or predict "stopping power" (or more specifically, "stopping probability"), the best we can do is look at which specific load has the greatest probability of causing the most damage when it hits the bad guy.
Yeah, I know some guy will always say "It's shot placement that matters most." True, but everybody knows that, and we are only considering loads which the shooter or LEO can be taught to shoot accurately and quickly. No amount of practice and training can guarantee good shot placement during a combat situation. We need to ask, wherever the shot hits whatever subject at whatever angle, after passing through any likely barriers, which load is most likely to produce the most damage given a minimum and maximum penetration requirement.
The FBI tests are not perfect, but they provide good usable answers which correlate well with actual experience. Use of these tests has resulted in vast improvements in ammo used for self defense and LEO.
:banghead:
