Yes, but while not valid, neither is the other. You can't derive a stopping power calculation that can be a predictor of real world behavior on the limited number of variable being considered. It is simply interesting, hueristic, but not valid for the real world. Your Colt 1911 version is equally valid in the real world. So what is the problem?
Historical data do not work either. So .45acp Hydrashoks produce one shot stops 96% or 98% of the time when just one shot is fired. Will you get the same results? Given that historical data and future events such as shootings are mutually exclusive, then what happened in the past does not mean it will happen in the future in the same manner and part of what makes them exclusive is the number of situationally individual variables.
You can work all the numbers you want for various calculations and you may have a great correlation, not causation, but correlation between high numbers (or low, depending on the type of calculation) and ability to produce stops, but it is only a correlation. When was the last time you saw a formula that took into account the health and mental state of the person being shot so as to determine the stopping power effectiveness?
Your calculation for the Colt 1911 was a spoof, but real world historical data would indicate the guns work well, not perfect, not uniform across the board, but your formula sort of seems to work, doesn't it? Correlation, not causation.
