I have a different slant on the tumbler issue. I clean ALL my brass before reloading, and for a couple reasons. Cleaned brass won't scratch your dies. A scratched die will mark every case after that until you either replace the die or have it polished out. Next, I can examine a clean case allot easier than a dirty case when looking for problems. And last but not least, I think they look good. Cleaned cases look better than factory cases and I like the way they look. Cleaning your cases is such a 'no-brainer', why would you 'not' do it? I've seen tumblers on ebay for under $50. And if it doesn't do any good, why do most reloaders do it? Just my 2 cents worth.