If you look up ".357 revolver" (or whatever you're thinking of) you can browse various sites that sell them and then go to that store in person to purchase it.
Like, what they'd ask you why you want it? Home defense, shooting range, want it for your collection, whatever. Answer their questions as honestly as you can, because gun sellers are the ones who stop the overwhelming amount of gun sales, not the background checks. If you've never handled a gun, say as much to them because they'll be able to tell when they hand it to you to hold before the purchase. They're usually pretty friendly, relaxed, and enthusiastic about new gun owners as long as you aren't appearing like you're a psychopath.
As usual with these kinds of threads I always put in this image and recommend at least .45 caliber or higher. 9mm if you know exactly where to aim. This is not representative of all pistol calibers, just the common ones. For example, there are .357 rounds that are much shorter and stubbier than the one in this image (.357 SIG are the ones that are short, about the length of a 9mm bullet but share the same diameter as .357 magnum). Anything below 9mm is a recipe for permanent brain damage and disability.
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