The one(s) I've seen basically operated by having the shot and other junk, fall off the end of a conveyor belt with air blowing through it. As the dirt is much lighter than the lead, most if not all of the dirt is blown away, leaving only the shot to make it to the bottom. Wouldn't be too difficult to make a smaller version of this, using a home made belt and a fan with adjustable speeds, picking the speed that worked best. I have better things to do with my time. Using a .410 and or 28 load, makes it go farther.
