I think a bigger factor in police switching to semi-automatics was the introduction to the Glock, which as I recall was the first "respectable", widely adapted

I think a bigger factor in police switching to semi-automatics was the introduction to the Glock, which as I recall was the first "respectable", widely adapted service handgun without an external safety. That, just point it and pull the trigger, like the revolvers the police were used to, something previous manufacturers apparently weren't willing to do. Now, I wasn't paying close attention to this at the time, since I was in localities where owning a handgun was impossible to impracticable and I'd already settled on another model for when I could buy them (M1911), but this would suggest it was a combination of ergonomics and a perception that a semi-auto without an external safety was safe enough for police (and also note things like the extra heavy "New York trigger), plus of course the superiority of semi-autos in combat, in functioning in dirty conditions, etc. (They are more likely to jam, but you can clear that in the field, a revolver jam is generally a job for a gunsmith.) I'm pretty sure this wasn't all that related to the 1986 FBI Miami shootout, the biggest conclusion from that was the correct observation that penetration is critical, in this case, through someone's arm and then into their vitals. Ballistics Nerd details: 9mm is much better than stock .38 Special, but inferior to the .357 Magnum, which had been a big thing since the 1930s, and could easily shoot lighter loads equivalent to 9mm or wherever you want to trade off recoil for power, an inherent advantage of revolvers. 4 of the officers were carrying .357s, one a .38, all loaded with a .38 Special +P over-pressure rounds, presumably the "FBI load", that falls quite a bit shy of 9mm. But 3 were carrying 9mms, and the FBI's answer was a very powerful 10mm round, which they then backed off to what became the .40 S&W, and now they say bullets have evolved enough that 9mm is OK (and cheaper, and many say easier to fire). All that said, the conclusions about the Miami shootout certainly didn't hurt police adaptation of semi-autos.