In the world of handguns, there are a lot of choices to make.
What caliber do you choose?
Do you want a revolver or semiautomatic?
Metal frame of polymer?
Single or double action?
Full sized or compact?
There are literally thousands of weapons out there, and choosing one for your character can be a daunting task, especially if you didn't grow up in a country with more firearms than people.
I'm not going to go into every little detail today. There's simply too much ground to cover, and I could probably write a book on any three of those points if pressed. Instead, we're gonna cover the broad basics. If you have further questions, you're welcome to PM me or post in the comments below.
Today, we're going to go over two considerations: caliber, and whether or not to choose a revolver or semiautomatic weapon.
There are literally dozens of different pistol rounds out there to choose from, and on the surface, many of them are confusingly similar. For instance, most everybody knows the .357 Magnum, but what about the .357 SIG? There's the .45 ACP, but also the .45 Schofield and .45 Long Colt. Is a 10mm better than a 9mm? What about a .50?
In the end, it all boils down to one thing: personal preference.
Yes, a .44 Magnum is more powerful than a .38 Special. Yes, the .45 ACP is more powerful than the 9mm. However, in a firefight, that doesn't really mean a whole hell of a lot. What matters is whether or not you can drill the target multiple times accurately enough to take them out of the fight. One shot one kill is fine for a sniper, but a pistol is not a sniper rifle. It is extremely difficult to put down a target with a single shot, and even if you can, you're an idiot if you don't put a few more rounds into the target just to be on the safe side.
Ammo is cheap, lives are not.
Practically speaking, you want to choose a weapon that suits your character's level of physical strength. A Chadra-Fan has no business handling a Desert Eagle, but a big human or a Wookiee would be just fine. A smaller human would probably be better off with a 9mm, because it's a light round that doesn't have a whole lot of recoil, and you can fit a ton of rounds in a magazine.
With that in mind, are there any practical advantages to a revolver?
Yes, but with caveats.
Unlike semiautomatic pistols, revolvers tend to have very limited ammo capacity, usually 5-6 rounds. Even with a speedloader, they take longer to reload as well. However, they do have a few things going for them.
Revolvers tend to be more rugged and reliable than their semiauto counterparts. You can also fire more powerful ammunition through a revolver, and since you don't have to worry about gas pressure, you can fire a wide variety of rounds as well.
However, all that is meaningless unless your name is Harry Callahan. It takes a great deal of skill to successfully employ a revolver on the battlefield. Remember: the name of the game isn't to blow their head off in a single shot, it's to put three or four rounds into the center of their chest. Unless you really are that good, and I only know of a few who are in an RP setting, you're better off picking a semiautomatic handgun suited for your character's size and strength.
If you're not sure what a good choice would be for your character, there are a few ways to go about looking. You can always resort to google; there are hundreds of websites that can provide all the information you need. Or you could ask me. I'll be happy to walk you through the steps to choosing a gun that's right for you.