I've found that the corn cob from pet stores is "flakey" while corn cob blasting media is "grity" (about the same as grits). I used the crushed walnut shells from PetSmart (lizzard litter) which worked much better than the "flakey" corn cob. I've tries a lot of different stuff for tumbling brass from dried coffee grounds, rice, beach sand, dried beans, wood chunks, and cat litter (diotomacious earth, aka oil dry) but the tried and true corn cob blasting media and crushed walnut work best. Best deal I've found yet is
http://www.drillspot.com/products/49...bs_blast_media. Twenty five and change with free shipping for 40 lbs. is pretty darned good...