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By Wayne McLerran
Updated: 5/8/16

For many years I’ve been using Dave Maurer’s 4mm x 5mm angle-cut ceramic
media to clean .40-65 & .45-70 BPCR cases in a Tumbler’s Model B tumbler.  
It’s always worked great.  I also have a relatively large ultrasonic cleaner (holds
1.3 gallons of liquid) with an internal heater and wondered how well it would
work for case cleaning.  And more recently, after reading several reports, I
decided to try stainless steel pin media in the tumbler.

Ultrasonic versus Tumbler with Ceramic Media
Always wondering which method was the best solution for cleaning BPCR brass,
I split up a batch of 200 pieces of very dirty brass.  They were fired with black
powder and allowed to set without cleaning and with primers still in place for
well over two years.  The brass was included with a rifle I purchased for resale.  
I will not cover the details of the test here but, from a speed and cleaning
perspective an ultrasonic cleaner is by far the fastest technique.  If the primers
are removed and the cases tossed in a soaking solution shortly after firing
, a
ultrasonic cleaner will finish the job in a few minutes.  Also, the ultrasonic
cleaner was much faster when removing the brass.  Just lift up the
wire basket
and dump the brass in a bucket or bowl of hot clean water to remove any
remaining cleaning solution residue.  But a good large ultrasonic cleaner is
significantly more expensive, several hundred bucks more, than a good tumbler
and ceramic media.  Another benefit of ultrasonic cleaning is there are no
limitations to case size or configuration.  It
will work just as well on
bottleneck or very small cases.

The cheaper tumbler and ceramic media approach does require more run-time
but will eventually accomplish the same level of cleaning for larger cases, and it
excels in improving the appearance of the outside of the brass.  To separate the
brass and ceramic media does require tapping and checking the inside of each
case to ensure no media is stuck inside.  A tumbler and ceramic media is not
recommended for bottleneck cases and may not be a good solution for smaller
cases unless smaller ceramic media is used.

Cleaning cases with ceramic media can slightly shorten the case due to
burnishing (peening) of the lip edge and roll over the lip edge.  When case
lengths are trimmed during the case preparation and reloading process, a
chamfering or deburring tool is typically used to remove metal burrs or whiskers
from inside and outside of the case lip.  Excessive chamfering will thin the case
lip which the ceramic media can easily burnish (wear down) or bend over.

By the way, Lyman makes a very nice line of ultrasonic cleaners and specialized
solutions targeted at the firearms and shooters market.  They recently added a
large (6.3 quart) ultrasonic cleaner to their current line.  For more details go to

Tumbler with Stainless Steel Pins
I’ve been using ceramic media to clean .40-65 and .45-70 BPCR cases.  The
cases came out shinny and spotless.  The insides were clean as were the primer
pockets.  So I was a happy shooter until I acquired a .38-55 Win. rifle along with
a couple hundred dirty cases.  Reports on shooting forums suggested that the
ceramic media I was using may not work as well in smaller diameter cases.  
Sure enough, after running the cases in the tumbler for a few hours, the primer
pockets and outside looked great, but the condition of the inside walls left a lot
to be desired, especially deep inside next to the primer hole.  Also, there were
some problems with the ceramic media wedging inside a few cases.  So a
decision was necessary if I intended to forego using my ultrasonic cleaner and
use the tumbler; look around for a source of smaller ceramic media or give
stainless steel (SS) cut wire pins a try.  By the way, Dave Maurer also supplies
ceramic media in smaller sizes (3mm x 5mm), reported to work well in smaller

Based on feedback posted on several forums, I decided to try SS pins.  SS pins
are very small in diameter, will easily clean the smallest crevices and slide
through primer holes without jamming up.  Since I also reload and shoot several
smokeless handgun and bottleneck rifle calibers there were additional reasons to
try SS pins.  If they work well for cases as small as .380 Auto than I’d have a
one-size-fits-all calibers-and-case solution.  But the results proved less than
satisfactory for large BPCR cases.

SS media pins are available in 5 lb bags from several shooting supply retailers
such as Midway, Brownells and Buffalo Arms.  A 5 lb bag is ideal for use in the
Tumbler’s Model B tumbler.  Smaller 1 lb bags are also available, mainly to
replace the media lost during cleaning and handling, more on this later.  I picked
up a 5 lb bag of Pellets LLC brand from
MidwayUSA.  Prior to discussing the
cleaning results, I should share some of the information found while researching
the subject.

Most folks are under the impression that stainless steel is nonmagnetic, which is
not necessarily the case.  Without going into a lot of detail on the subject, there
are different types of SS alloys.  The composition of the alloy, the manufacturing
process and the resulting crystalline structure determines the magnetic properties.  
Generally, when the alloy contains a significant amount of nickel, the resulting
crystalline structures are less magnetic.  If manganese is used rather than nickel,
the austenitic crystalline structure is more magnetic and the SS is cheaper to
make.  Pellets LLC’s brand of SS pins are magnetic.  I understand the SS pins
Brownells and Buffalo Arms are also magnetic.  Due to the size, being
magnetic has advantages.

The Pellets LLC brand pin dimensions are approximately 0.250” long and 0.040”
in diameter, not much larger in diameter than a sewing machine needle, but much
shorter.  They’re small enough that I actually found a few attached to small
bubbles and floating on the water surface.  The surface tension and air bubbles
were sufficient to keep some of the tiny pins from sinking, similar to the
property that allows small insects such as water striders to walk on water.  
Here’s where the magnetic properties are an advantage.  It provides a way to
pick up spilled pins.  There is no way that you will clean a bunch of brass and
separate the media without dropping or spilling a few pins.  And you will be in
“deep doo-doo” if you drop a few on the carpeted floor and the wife of kids step
on them.  My office and loading room (converted bedroom) has carpeted floors,
and a strong magnet did a great job of picking up a few I spilled.  So how well
does the pins work?

With the 5 lbs of pins in the tumbler, lots of water and an ounce of Dave Maurer
brass cleaning concentrate, various handgun and bottleneck cases were cleaned.  
They all came out looking brand new, inside and out with completely cleaned
primer pockets.  Here are a couple of YouTube videos that provide a visual
detail of the process:
At this point I was completely “sold” on SS pins, but later uncovered a
significant problem when cleaning larger BPCR cases.

Case Lip Peening
After cleaning a batch of .40-65 cases with the tumbler and SS pins, it became
clear that the lip or edge of the case mouths were expanding (flaring out and
rolling over in both directions, but mostly to the inside) as much as 0.004” wider
than normal due to a peening effect which I had not noticed earlier when cleaning
the handgun cases.  And peening had never been a problem when using ceramic
media in the tumbler – more on this later.  To determine if the water level in the
tumbler was a factor affecting the amount of agitation and the rate of peening, a
short experiment was conducted with two batches of 25 new .45-70 cases.  One
test batch was with the water level only covering the pins (low-water test).  The
2nd test batch was with the tumbler filled with water to within 1” of the top.  The
case lips were peened in both tests, but to a lesser degree with the tumbler
almost full.
Note: Closely inspecting the previously cleaned handgun cases indicated the lips
were peened which I had overlooked at the time.

After reporting the test results on a couple of BPCR discussions forums, some
shooters responded that the peening was due to using stainless pins with
Thumler’s high speed 3,000 rpm motor, the motor installed on my tumbler.  The
slow speed (1,550 rpm) motor was recommended to eliminate peening.

The slow speed motor was ordered and installed and the worse-case low-water
test was repeated.  It quickly became clear that peening was not eliminated but
was significantly reduced.  Further testing indicated the slow speed motor
resulted in less drum noise and required more run time to clean cases, neither of
which was a surprise.

Later, I ran the same tests as above but with 7 lbs of Dave's Maurer's large
ceramic media with 50 .40-65 Rem. cases in a Thumler's Model B with the hi-
speed 3000 rpm motor. Several case lip thicknesses were measured with the
measurement locations identified. Measurements were taken at 2 hr increments
over 6 hrs. The drum was filled with water to just over the media and brass, so
the drum was a little over half full.  No measurable peening was detected, but
read on.

Sometime later, after annealing the case necks, peening was evident with ceramic
media.  Annealing apparently softens the necks sufficiently for peening to result
even if using ceramic media.  Following the purchase of a very nice annealing
machine I now anneal cases prior to every reloading and have noted an increased
rate of case lip peening, but believe the benefits of annealing are greater than the
negatives associated with lip peening.

Due to additional testing there’s no question in my mind that peening is definitely
due to rotary tumbling.  And the rate of peening is determined by several factors:
brass softness, rotational speed of the tumbler, type of media, how full the
tumbler is loaded, how long the dirty brass was soaked prior to tumbling and
finally the tumbler run time.  If someone tumbling brass with ceramic or stainless
media does not believe peening is taking place than they have not measured the
lip width close enough before and after removing the brass from the tumble.  The
slight rolled over edge may not be sufficient to cause a problem or shorten the
cases appreciably, but one cannot tumble brass with ceramic or stainless media
without some peening taking place.

Dave Maurer, the supplier of ceramic media to many shooters, suggests using
tennis balls in the tumbler to eliminate peened lip edges.  He says to fill the
tumbler full of tennis balls after putting in the media and brass.  The tennis balls
prevent the brass and media from falling far enough in the tumbling process to
peen.  Some have suggested that peening will not happen if the tumbler is filled
to the top with water while others say to only add enough water to cover the
media prior to adding the dirty brass.

As noted earlier, at one point in time I concluded from testing that stainless pins
caused peening and ceramic media did not, but have since proven to myself that
was an incorrect conclusion.  The rate of peening can be significantly reduced
using some of the techniques mentioned above but it will not be completely
eliminated when using a tumbler.  To date I have “played around” with all the
variables including switching back and forth between ceramic and stainless,
purchased a slow speed motor for my Thumler’s; adjusted the tumbler liquid
levels, media levels & brass levels; adjusted the frequency of annealing and paid
close attention to run time.  I tried Dave Maurer’s suggestion of using tennis
balls and even tumbled only brass (no media) in plain water and was able to
measure peening.  As the case lips bang against the media and other cases, lip
edge peening is unavoidable.  The result is I have proven to myself beyond a
shadow of doubt that I can control the rate of peening but it is inescapable, i.e.
peening cannot be completely eliminated when using a rotating tumbler.  The
only methods I know of to eliminate peening is to use an ultrasonic cleaner or a
vibrating-style tumbler.
Note - For details on techniques to remove the peened edge see the article titled,

By the way, regardless of the cleaning technique used, there are at least a couple
of ways to quickly dry the wet cases.  I’ve tried the towel and hair dryer
technique, but prefer standing up the cases in a large frying pan and heating them
on the stove top.  Turning off the heat when the water vaporizes ensures the
temperature is well below the range that will damage the brass or result in
discoloration.  If you’re in a rush, just aim a small fan at the pan and they will be
ready to handle in a few minutes.  The same technique can be used for the SS
pins if you prefer not leaving them wet when stored in the tumbler drum.  
Attempting to dry ceramic media using the same technique will work but will
take a lot longer since ceramic is a poor conductor of heat.  Since I’m usually
cleaning brass at least once a month I just store the wet ceramic media in the
tumbler drum until it’s needed.

Wishing you great shooting,