Mr Beta,
Looks like it works just fine, maybe not as good as other stuff but in an "emergency" it'll work and apparently no harm is done to the cases. And, you could test further using assorted kinds of sand, and longer times.
I don't use a tumbler because I don't mind a "patina" on my cases, I just want them squeaky-clean which they are when I get done washing them.
But reading posts from all the "experts" here, I thought you'd be showing in the "after" pic an open hand but with no cases in it...because they were worn completely away and had disappeared.
Remember, there are ALWAYS naysayers like Snuffy...that's pretty average/common thinking and 75% of the world is made up of average limited "thinking" people.
For the rest of us not so afflicted, thanks for the info.
Now, make the others -- and possibly your tumbler -- happy and go buy some "appropriate" media to use.
-- John D.