Brass and aluminum are more maliable than steel. Steel casings will prematurely wear the chambers and the headspacing in the cylinder. When the round is fired the gases expand the casing to form to walls of the chamber gripping inside of the chamber walls. This is less so with steel casings and will cause excess pressure on the firing pin bushing from the casing head being pushed back into it with excessive force.
I dont know of much 38 or 357 ammo that is steel cased. What brand of ammo are you using?
I'm already surrounded by half-dead brainless people already, the zombie apocalypse would just give me a reason to be productive and get rid of them.