I bought some (2500) once fired 223 brass from a source that I have purchased from before without any problems. This time, however, the brass had green corrosion inside and a few (hundred) had stuff stuck to the outside which looked like gum and sand.
Long story short, I bought the steel media and the Thumler's rotary tumbler and ALL the brass looks factory new. And, now I can see a few cases that show signs of head separation.
I am very pleased with my purchase although it does add a few minutes to my case prep. But, reloading has become a hobby for me so I am not concerned with rushing through the process.