One note: you can use a .38 caliber bullet in a gun chambered for .357 but not vice-versa. The bullets are the same diameter but the brass cartridges of the .357 bullets are too long to fit in a 38 caliber gun.
Lots of folks use .38 ammunition to practice with in their .357s. It is cheaper to begin with and there is lots of cheap surplus type ammo around. To practice with that is.
Back when I was into guns and liked to blow up bottles and cans and shoot at targets and such, I had a .357 Ruger that I liked a lot and kept a couple of boxes of really good stuff around "just in case" - like Talon P+P armor piercing hollow points. Pretty potent stuff.