The killing power of the 357 mag in revolvers is well known. The 9mm is not as effective.
I read about a man who worked for the police morturary, state that it took numerous rounds for a 9mm or 38 auto to kill a man from his experience. He said the 45 ACP or 357 magnum killed with less shots.
At the time of the original regulation the police used revolvers and there was a prejudice against semi auto pistols.
The semi auto is now the preferred weapon rather than a revolver. There are pro and cons for each one.
The fastest shot is with a revovler and the speed is incredible. Check you tube for videos.





