Recent testing of the three major police and military calibers by the Federal Bureau of Investigation found that the .45 ACP was no more effective with regard to terminal ballistics than either 9 x 19mm Parabellum or .40 S&W. After two years of testing, one of the final FBI comments was that services that adopt (or stay with) .40 S&W or .45 ACP did so at the risk of increased recoil and a possible reduction in accuracy as 9 x 19mm with premium quality ammunition had nearly exactly the same performance.
Yeah but the wiki says the following,
Recent testing of the three major police and military calibers by the Federal Bureau of Investigation found that the .45 ACP was no more effective with regard to terminal ballistics than either 9 x 19mm Parabellum or .40 S&W. After two years of testing, one of the final FBI comments was that services that adopt (or stay with) .40 S&W or .45 ACP did so at the risk of increased recoil and a possible reduction in accuracy as 9 x 19mm with premium quality ammunition had nearly exactly the same performance.