Jim, no, the Rock Island M200 can only shoot 38 special. The 357 mag is longer so it won't fit and has higher chamber pressure, so even if it would fit it would be unsafe to fire. The Rock Island M200 is rated for +p ammunition though, so you can fire 38 special +p threw it. Sorry but hope this helps and you're very welcome.

Jim, not if the Pistol is chambered in .38 Special. Only if it is chambered in .357 Magnum can you use both Magnum and .38 Special otherwise, .38 Special only as .357 Magnum won't chamber in the shorter .38 Special Chamber. Cheers and stay safe!

When you say mag ammo I assume you meant .38 special right as there is no .38 magnum. If so then yes you can with nearly all .38 guns, but with some the case might be a bit tight so I would ask the manufacturer themselves.To be sure. rkguns.com/rock-island-armory-m200-38-special-full-size-revolver-51261.html if you meant .357 magnum NO it will not. You can shoot 38 out of a 357 but not vice versa https://winchester.com/Blog/2020/10/27/13/56/The-38-Special-Vs-the-357-Mag Stay safe.