Dogngun is absolutely right.
I've been shooting my Ruger GP-100 for over 10 years. Never had a problem with seating .357 ammo, after firing .38 ammo, if the .38 ammo was of good quality.
However, if you buy cheap, off-brand reloaded ammo often found in gun stores and gun shows, you'll likely get lousy ammo: soft lead bullets, poorly cast bullets, mediocre or too little lubricant on the bullet, primers not fully seated in the back of the case, etc.
An exception to not having a problem with .38 Specials creating a ring of lead in the chamber may be brand-name 148 grain lead wadcutter ammo.
The Big Boys (Winchester, Remington, Speer, Federal) all use very soft lead for their wadcutter target ammo, because the bullets are swaged under pressure and not cast. Long-term use of 148 gr. wadcutters can create a ring of lead in the chambers, that may make seating .357 ammo difficult.
However, a good brushing with a bronze brush usually removes it quickly, or reduces it so .357 ammo can be seated.
The reasons the semi-auto .357 Magnum has never been wildly popular are many:
1. These handguns are expensive, compared to a revolver.
2. Like all semi-auto handguns, they are designed to work within a certain pressure level, and bullet weight. Stray outside that, up or down, and problems appear and reliability is affected.
3. They are large and bulky, often ill-fitting in the hand.
4. Like all semi-autos, they are dependent upon perfect ammo and --- many often forget this --- perfect magazines. Damage the lips of a magazine and you're in for some aggravation.
5. Reliability will never be as good as a revolver.
6. Lead bullets are not recommended, so you're stuck with jacketed bullets.
The classic .357 Magnum revolver has it all over the semi-auto .357 Magnum. You can load it with very light loads. I used to load a 75-grain wadcutter to a little more than 400 feet per second, to introduce newcomers to shooting. This gives little more than a "Blap!" but puts an easily seen hole in the paper target.
Dogngun has given sage advice: A Smith & Wesson or Ruger .357 Magnum. 4-inch barrel. Adjustable sights. Perhaps made of stainless steel but that's not absolutely needed.
And make sure that the revolver you buy, if it's used, can be used single and double-action. Some police departments and shooters will change the revolver to double-action only.
Double-action means that you pull the trigger and it cams the hammer back, rotates the cylinder and -- if you continue pulling the trigger --- drops the hammer on the cartridge.
Single-action means you have to manually reach up and pull back the hammer, for each shot.
Get a double-action revolver, and you can shoot it both ways. It's also easier to load and unload because the cylinder swings out to the side and empties can be ejected all at once, instead of one at a time as in a single-action-only revolver.
Start your shooting with light .38 Special loads. Then move up to the standard .38 Special load of a 158 gr. lead bullet at 850 feet per second. After you're comfortable with that load, move up to a .38 Special Plus-P load, using a 158 gr. lead bullet.
Finally, move up to a .357 Magnum load, if you wish.
The ol' 357 Magnum (it was introduced in 1935; Gen. Patton carried one in World War II) is still the most versatile revolver round out there. And if you reload, you can tackle everything from mice to large deer with it.
