After spending several years as a deputy, and almost as many as a range instructor, I was really hard pressed to let go of my revolver.
But, the transition to autos was forthcoming and inevitable.
At the risk of bashing the revolver lovers (which I was one), I could see the combat, or confrontational benefits of the auto in comparison to the revolver. So at the orders of my superiors, I designed an auto transition course specific for our needs with the help of FBI and US Marshall instructors. The course had to be lawsuit proof as much as possible, and had to be approved by the Sheriff & Co. Attorneys, so it was fun.
Most officers (including ours), but not all, rarely shoot their guns unless qualifying. And they clean them even less. Then you have the smaller percentage that shoots and cleans them regularly. They become very proficient in short order. We had implemented the minimum carry calibers, but it was like most others I read here, carry what you wish as long as it meets minimum requirements, and you can qualify with it.
I was one of the last to change from the revolver as it did the job very well, but eventually I did so. Prior to the release of the P85's, I obtained two from Ruger for testing. One of which I bought back afterwards.
I carried that on duty for about 3 months.
At the time I also inacted an ammunition change to Winchester SilverTips in all calibers. The tests and performance levels were leaps & bounds over what we had at the time.
I was so unimpressed with the 9mm (no offense to 9 lovers) after numerous shots into enraged livestock, or injured deer, etc., especially after carrying the .357, that I started to test .40 S&W's and .45ACP's.
The .40 had a better showing than the 9mm, but less than the magnum. The .45ACP using 185gr. Silvertips was visually "on par" with the magnum. But I eventually settled on the .40 S&W with 155gr Silvertips, which ended up as a good balance between capacity and performance.
It seemed only slightly less than the .357 & .45, but with a slightly larger magazine capacity. My gun of choice was a Mod96 Beretta.
I liked the heft & feel of the gun much better than the Glock and it still had the ability to shoot cast for practice.
The 10mm would've probably been my first choice, but there wasn't a large selection of models back then. S&W 1006's, or Colt's Delta Elite's were about it, and Smith was having QC issues back then.
My 2 cents.........
Take care,
Bob