I've once been given a lot of .45 acp cases that had beenstored in less than ideal conditions.Long story short,after tumbling 4 hours with lots of car polish in the media,I recuperated aprox 50%.My standard is if I get my finger over the stain and I feel some resistance,I scrap it( brass recuperation).If it is so smooth that I can't feel the difference,I guess it won't damage the sizing die or the chamber of the gun it is to be fired into.