[308Loader]

hello. I think I may have done a bad thing. I just got an ultrasonic cleaner for my brass. works great! cleaned some cases ultra fast. the expander ball in my fl size die had a build up of junk on it, so I tossed the fl size die in to the tub after cleaning the brass. the die came out black. when I rubbed it with a rag it looked copper ish. did I just ruin my die, or plate it in brass? time for a new one?

it is now in the tumbler with some walnut trying to clean it off. help