I do the same. Anything from a target .38 Special loaded wadcutter up to full bore goes in .357 brass. I pretty much only use .38 Special brass for .38 revolvers. I like to shoot .38 loads before I shoot .357 magnum loads and I don't like taking range time to brush out the cylinders. Using .357 brass eliminates the problem.I load 14.6 grains of W296 behind 158 SJHP in my Model 19s, and 5.4 grains of 231 behind 158 gr LSWC. These are probably not much more than 38 +P loads, but the target has holes in it just the same.
edited to add that these loads are in 357 brass.