I bought a Lyman tumbler that came with 3 bags of this green colored Corncob tumbling media shown in the photo below. Obviously it's treated with something, but I don't think it does that great of a job at shining up .45ACP brass. For you folks that have tried various different types of cleaning / polishing media in your vibrating type tumblers ... do you think crushed Walnut shells like you find at the pet shops does a better job than Corncob? If you use crushed Walnut shells, do you find that the coarser shells do a better job that the real fine ground shells? Maybe a 50% / 50% mix of both Corncob and Walnut shells? BTW ... I don't worry about the media getting into the primer pockets, since I de-prime after it gets out of the tumbler. Thank's, .