Fill your tumbler with media made from corn cob, walnut or a combination of both.
Place non-damaged bullet shells in the tumbler.
Turn the tumbler on and allow it to run until it completes a cycle. Most tumblers have cycles that run three to four hours, but depending on the brand, the cycles can run anywhere from two to 12 hours.
Remove the bullet casings. Inspect the shells to ensure no damage has occurred while they were cleaning. Proceed to complete the reloading process.
Cleaning Without a Tumbler
Mix 3 cups water with 3 tbsp. lemon juice and 1 tbsp. liquid dish soap in a bowl wide enough and deep enough to hold your bullet shells. Stir the mixture.
Place the bullet shells in the mixture. Let them soak for two hours, stirring them around occasionally.
Remove the bullet shells from the mixture. Remove excess moisture using a towel.
Place the shell casings on a cookie sheet, or other oven-safe, flat surface. Pre-heat the oven to a low oven temperature, around 150 to 200 degrees Fahrenheit. Place the bullet shells in the preheated oven to dry for around ten minutes. Remove the bullet shells from the oven. Allow them to thoroughly cool.