And the winner is corn cob! I recently got a Thumler's Ultra-Vibe 10 tumbler, and with it came a fresh batch of corn cob media. I didn't have any cases to tumble, so I decided to experiment with some surplus Greek HXP .30-06 I had already tumbled in some fresh walnut media in a friend's tumbler. The corn cob, with about a teaspoon of Mother's Mag Wheel polish in it, took the cases from just OK to looking like brand new brass! I didn't think cases could get this clean without the use of a rotating wet tumbler with stainless steel media. I do however understand why folks would want to use crushed walnut for doing smaller calibers. The corn cob definitely has a larger granule size and could easily get stuck in smaller necked cases like .223 or .22-250. On the left is the brass tumbled in walnut- good but not great. On the right is 50 rounds of brass from the same batch looking super-clean after tumbling in corn cob media. Now I need to load up on some cheap bags of corn cob.