Monkey those groups sound too good, some psyche is probable, as you were using them first time ? Have faith in your own abilities my friend...and check sights tightness !!
I also suggest you check the diameter and type of projectiles you are using and slug your barrel diameter to be compatible [rather than the cases, but check them for splits.] A chronograph for a 38Spl should be 650-900FPS - but your load seems OK by me and an up to 4" group not un-usual at 50m especially for the ballistically inefficient '44 Gallon barrel' W/Cutter!
Try again after digesting above ...and good luck, enjoy your research !