Gun enthusiats - what is this device for?

Just watching Tremors. At that bit where the survivalist-types first meet the creature in their basement I was struck by a device they had on the workbench. It was a vibrating plastic dish with a lid. Inside was what looked like sawdust and the were tipping ammunition into it. What is it for? My best guess was to polish the ammo. Is that correct? Why would you need to do that - reduce the risk of jamming maybe? I googled a few gun retailers but did not see anything which resembled this device for sale. I am quite ignorant where guns are concerned, but curious nonetheless.

It’s a brass tumbler. The brass is cleaned before the reloading process starts.

Clean brass is easier on the dies, and makes resizing easier.

Do you mean reloading used cartridge cases? I didn’t know you could do that - shows what I know huh :o

Yes, many used cases can be re-used. You wouldn’t reload the steel cases or other non-brass cases, and you don’t reload Berdan-primed cases. (Berdan-primed cases have two ignition holes, while Boxer-primed have one. I suppose you could remove a Berdan primer hydraulically, but why not just use Boxer cases where the old primer can be pushed out with the pin on the die?) They wear out after a few reloads.

Notice that at the beginning of the movie Michael Gross’ character is complaining about the mail-order ammunition down at the general store so he’s obviously a particular fellow.

Not 100% sure about the big double-barrel gun that he totes, I assumed it was either something like a .600 Nitro Express or one of the larger (4 or 8 gauge) shotguns firing solid slugs, but that kind of ammunition is going to be rather pricey and hard to buy through the mail so right there he’s probably in the habit of loading his own.

Correct me if I’m wrong but isn’t crushed walnut shell one of the polishers of choice?

It is - does a nice job (inside a tumbler) of cleaning cases, and lasts a long time.

Nickel cases are no problem.

Those tend to be nickel-plated brass.