For way to long I’ve used crushed walnut sold by Harbor Freight as blasting media. Very dusty and the pieces were stuck in most of the flash holes after tumbling.
Very glad I decided to try this from Amazon. Very minor amount of dust and fine enough not to stick in flash holes.
https://www.amazon.com/gp/product/B001OVGPH6/ref=ppx_yo_dt_b_asin_title_o06_s01?ie=UTF8&psc=1
