Technically, a dry tumbler is
a vibrating bowl cleaner. This device consists of a covered bowl-shaped
hopper with an electric motor mounted to the bottom. The motor has an
offset weight installed on its shaft. When the motor is on, the offset
weight causes the motor and bowl to vibrate. The motor does not spin the
bowl - its sole purpose is to create vibration.
There are two common types of tumbler media: corn cob and
walnut. The corn cob based media will leave a high gloss finish on the
takes longer to clean while the walnut will leave a satin finish. The Corn
cob media is the same used in sand blasting; the pith and the chaff of the cob
have been removed, leaving only the woody ring, which is then ground up and
screened for size.
Many people will try to skimp by using cat litter or pet
bedding made from corn cobs.
Since these use the entire cob and not just the
woody ring, they will leave your tumbler a mess and result in clogged
bottleneck rifle cases.
Ground walnut shell is more
aggressive than corn cob, so it cleans faster. Unlike corn cob, ground
walnut shell pet bedding makes an effective tumbler media. This is sold
in pet stores for use in reptile enclosures. Both media types, however,
from sand blast supply houses in 40-50-pound bags.
Polishing compounds can be added to the media to assist in
cleaning and help to keep the dust down. Liquid polishing compounds are
available from reloading supply houses and tumbler manufacturers. Lucas
Oil Outdoor Line’s Gun Metal Polish is an excellent product that works great in
dry tumbling media. Add about 1/8 cup of
liquid polish to the media (or up to 1/4 cup for large tumblers) and allow the
tumbler to run without cases for about 10 minutes to distribute the polish.
To help the media stay cleaner longer, some reloaders will
also add used dryer sheets cut into strips to the media. These are
discarded and replaced at the end of each run, taking a good bit of
powder/primer residue and dust with them.
It’s always good to refer to your specific tumbler’s manual
for usage instructions. However, here’s the gist of how a dry tumbler works.
The tumbler is filled to about 2/3 capacity with dry
media, filled the rest of the way with dirty cases sorted by caliber, and then
run for several hours to clean the cases. It is not necessary to remove
the spent primer from the brass before tumbling, as dry tumbling will not clean
the primer pockets anyway (or even the insides of the cases). Once
cleaned, the cases are separated from the media, and can be reloaded
Safety and Hygiene
In addition to grit, debris, and tarnish, the
tumbler removes powder and primer residue from your cases. This residue
ends up in the media. Primer residue contains a poisonous chemical
called Lead Styphnate which can contribute to elevated blood lead levels.
The best way to avoid exposure to this toxin is to handle the media (and
dirty cases) as little as possible. A media separator can help with
In part two of our series on
case cleaning, we will be
looking at wet tumbling.