At least 10 years ago I bought a 50# box of untreated corn cob grit from Kramer Industries in NJ. Shipped to my house, it was $104 all-in. They offered a variety of grit sizes, and I got the 14/20 grit size. It has done fine work as untreated media by itself for CLEANING brass cases, but its polishing ability is minimal. It does OK for my spoiled-rotten over-indulged totally-pampered brass that starts out as new Starline cases and never sees mud, snow, rain, or saltwater. It worst environment is dry desert dust, and for all I know that might be what helps give the brass the small bit of polishing it does get. 10 years in, I have about half of that media on a garage shelf in reserve.