Disapointed in my first run with walnut shell media in a rotary tumbler. A 5 hr. run did very little,as far as removing tarnish\corrosion. Probably could get the same results wiping the cases on my shirt tail. These are .357 cases, probably been reloaded 2 or 3 times, and they are of varying vintage, some probably 4 or 5 yrs old. Stainless media would work,but I have a bag of sand in the garage that would probably do a fine job also, if I don't run them too long. Nobody seems to do this, though, and there's probably a good reason- What might that be?