It is rifle dependent. The Henry/Winchester early designs have very little problem with .38s vs .357s, the carrier moves vertically, not at an angle, so you don't have to worry about feeding problems. Most of the other designs have angled carriers and a feed ramp so they don't like some forms of ammo. Lots of magnums will feed specials, but it is not guaranteed. Usually if they won't feed both, a good smith can fix them so that they will.