The semi-autos in my collection are made for .25 (6.35mm), .32 ACP, .380 ACP and .45 ACP. Note: ACP is the acronym for Automatic Colt Pistol. In the revolver category, I have handguns chambered for .22 Long Rifle, .32 NP (New Police), .38 Special and .357 Magnum. The Colt .32 NP (flat nose) is functionally the same as .32 S&W Long (round nose). And finally, I have a combination over/under gun that fires .45 Long Colt and .410 Shot Shells. In 2022 I added an S&W .41 Magnum.
The only 9mm I've ever purchased or owned was the Colt All American Model 2000. It was short-lived, as I gave it to my son within two weeks. The .40 S&W has gained in popularity since its debut in January 1990, but I personally have never owned one. UPDATE: In 2022 I purchased this SIG Sauer P320 AXG Classic. If I had to choose a favorite caliber, it would be the .45 ACP. I currently have three handguns and one carbine that fire that cartridge. I have three revolvers that fire the .38 Special and two that fire the .32 New Police. There are two .380s and two .32 ACP pistols. So these are the most popular calibers in my collection at this time.
Technically, my .357 Python will fire .38 Specials so I could have included it in that count, but I never fire .38s in it. I've written before about all of my friends firing my old Python, but in real terms, it hasn't been fired a whole lot. And it's not because I don't have that many friends. My good friend at the gun store was telling me about his neighbor and three teenage kids burning through a thousand rounds within a few hours the other day. I don't do that. A big day at the range might consume 200 rounds of .45 ACP ammo each if my two son-in-laws are with me and I buy it in bulk for $100 bucks per 200 rounds.