I don't know what the corn cob is (been in a bucket for years) but the crushed walnut shells is '24 Grit Fine Soft Abrasive' according to the box...I used it a couple times for blasting, but it wasn't as good as the glass beads [for blasting]...IIRC, the glass beads were expensive...
Edit: I was curious as to whether cutting/resizing/bottlenecking would flake the plating off...It didn't...
