For handloaders, brass is both costly and reusable; making spent cases at the range feel like loose change just waiting to be scooped up. Pistol brass is like finding dimes and quarters; rifle brass can be worth a dollar or more. For some, scavenging brass is a hobby, a kind of modern-day gold panning, but with better returns. You never know what you might find, but usually you’ll always find something. To be honest, for me, it is a miniature hobby, and I have found everything from spent 45-70 casing to spent 4.6x30mm brass.
If you plan on reloading that brass, then the first step is to clean it. Right now, wet tumbling with stainless steel media is the popular option. However, for the longest time tumbling in vibratory tumblers was the go-to method for cleaning cartridge brass, and it still is part of the process for some hobbyists and larger scale ammo remanufacturing. Much of this is logistical as scaling up wet tumbling methods is difficult, disposing of water containing heavy metals, and drying brass once it has been tumbled all can be done relatively efficiently in the small scale but are more difficult once scaled up. For this reason, dry tumbling is still the primary means for cleaning cartridge cases for ammunition manufacturers.
Most handloaders who have investigated dry tumbling know there are primarily two tumbling media that are used. Corn cob Media and Walnut shell media, but what most handloaders do not know is that it’s not one or the other type of choice. To make the most out of your vibratory tumbler, you should be using both.
Walnut Shell Media
We do not think of tumbling the same way we might think of sanding, but it is very much the same. Walnut shell media comes in different “grits” which determine the average particle size. 12 Grit, or more precisely 12 Mesh, means that 12 openings fit within a linear inch of screen resulting in particles roughly 0.083 inches across. Another common size is 24 grit which is 0.041in average particle size.
As you can see in the magnified image, walnut shell media tends to have lots of jagged and sharp edges. This abrades the surface of the brass shell and makes for excellent cleaning action. It scrapes off carbon, and dirt, leaving behind the brass shell. With a Brinell hardness around 3, walnut shell is far softer than brass (which typically ranges from 80–100), ensuring it abrades grime without damaging the case.
Walnut shell media is the best choice for cleaning brass fresh from your most recent range trip. It is not going to leave the brass case with a “show room finish” but it will clean it to where you do not need to worry about dirt or carbon ending up in your reloading equipment.
Walnut shell media does not break down as fast as corn cob media, and it is not as porous. While you can add rouge to walnut shell media, I do not recommend it. The rouge gets everywhere and in everything. You need to tumble it in some media free from the rouge to get it off before you move it over to the press. In my opinion it’s not worth it.
It’s also not worth “charging” or treating walnut shell media with an additive. Unlike corn cob media, walnut shell media is not very porous and is substantially harder than corn cob media. Additives like NuFinish which work in corn cob will not perform the same in walnut. It may still coat the outside of the media, but it does not soak in or embed as effectively.
With Walnut shell media, if the brass isn’t coming out clean after a 2hr tumble, it is likely time to replace the media.
Personally, I purchase my walnut shell media by the 25lb box at Harbor freight. It will fill a standard 5-gallon bucket to the brim, and last about a lifetime of tumbling. Last time I purchased some it was about $27 all in. I generally prefer the 12 grit as it is less likely to pack into the primer pockets than the finer 24 grit.
Corn Cob Media
Corn cob media is quite a bit softer than walnut shell media, and it is more porous. It tends to be more rounded and does not have the sharp points that the walnut shell media has. corn cob media by itself does not polish or clean cartridge brass very effectively. However, because of its soft and porous nature it does soak up pretty much anything you pour in. It is an excellent choice for cleaning case lube off cases after sizing. It will soak it up and leave the clean of all but trace amounts.
With corn cob media you must “charge” or treat the media prior to use. There are many different options out there, pretty much every company that sells tumblers and media sells their own proprietary blend of wax, oils, and abrasives that get added to the corn cob media. The directions are pretty much all the same, add in a couple teaspoons per pound of media, turn the tumbler on and let it run for five or ten minutes before adding the brass in.
Corn cob readily adsorbs these additives, which usually include some kind of super fine polishing compound. This polishing compound is harder than the brass. Each particle of corn cob media becomes a miniature piece of sandpaper. As the tumbler runs the treated corn cob media polishes the brass and leaves it with a very shiny exterior.
Corn cob does break down and can become dusty. If you find the media is dusty, it means it has dried out and it’s a really good time to look at adding in an additive. NuFinish, a product intended to be used to restore the luster on automotive paint, is a mix of waxes, oils and some very fine abrasive is an inexpensive and readily available additive. A few tablespoons per pound of media is plenty, more doesn’t equal better. Fill the tumbler about 2/3rds full with media, add in the additive, and run the tumbler for about 10 to 15 minutes before you put the brass in. The oils and waxes will help bind the dust to the media.
Since the corn cob media is the final “Finishing” tumble, I tend to be a bit pickier with how dark I let it get. It’s not all carbon and dirt from the cases that makes the media turn a darker shade. If you have ever polished brass before you know your polishing cloth will turn dark. Brass will oxidize and turn black especially when mixed with the oils and waxes in the polish. This oxidation can end up as a very fine film on the polished brass which can be wiped off easily with a clean rag, or by adding a 3rd tumble in straight clean corn cob with no additives.
Either way, when your corn cob media is closer to black than to white, it is probably time to consider replacing it.
Brass Prep Prior to Tumbling
This is entirely up to you and your process. However, I generally decap everything prior to tumbling. There are two reasons for this.
First, it gives me a chance to inspect every case prior to just throwing it in the tumbler. Sometimes you’ll find rocks, dent, cracks, filled with dirt, or that the brass is Berdan primed. I have a rule of thumb that every case I handle gets a quick inspection prior to that operation. By following this rule every piece of brass gets inspected four to five times before it gets seated with a bullet. It’s a simple glance down, or rolling in your hand to look for issues, nothing elaborate. It’s a simple step that helps cut down on the amount of “scrap” brass that could cause an issue at the range.
Secondly, I like to have clean primer pockets. In the photo above I purposely chose a case that was not “picture perfect” clean to compare against a “dirty” primer pocket. This is to show what I consider “good enough”. I have plenty of examples that are about as clean as a factory new case. Reality is, you’ll get primer pockets that are as clean as a whistle and some that are just a bit off. That is regardless of what tumbling method you use.
In my opinion walnut shell media does a pretty darn good job of cleaning primer pockets. It’s a tough area to clean well, and if I see that primer pockets aren’t getting clean in the two-hour run time, that can be an indication the walnut media is worn and needs to be replaced.
Run Times
I used to be the guy who ran his tumbler 12hrs or more. I wanted to get things so clean and so shiny that I could see my reflection from the next county over. What I did not realize was that I could get largely the same results if I used the media as it was designed to be used.
Most of the work is done in the first two hours, both with the corn cob media with walnut shell media. After that the results are diminishing, and all you are doing is breaking down the media faster. I have gotten to the point where I have my vibratory tumbler set up on a programmable switch. I set when and how long I want the tumbler to run and load it all up and go on to the next thing. Usually it switches on at 2am, runs for 2hrs and then shuts off.
It is important to have a consistent run time when cleaning. 1hr, 1.5hrs, 2hrs, it’s up to you, just pick a time and stick with it. It’s hard to judge the health of your media if the run time is a variable. That is one of the reasons I like the programmable switches so much, I can set and forget.
If the brass is not the level of shine I want, I first check to make sure my wife did not shut it off (sometimes she’s up in the early hours of the morning). Provided that did not happen, I checked the condition of the media. If I am not getting the results I want, it’s time to either change the media or perhaps charge it.
Challenges with Dry Media
While I am biased toward dry tumbling, it would be unfair not to point out some of its challenges.
Media Separation
Media separation is not always as clean as it is with Stainless Steel media. There is just more dry media, and sometimes it can bridge in a case and be stubborn about coming out. corn cob media in the 12/20 grit range likes to pack primer pockets and will often block a flash hole.
You must inspect your cases and use a pick, or a universal decapping die to knock out the media from the flash hole and the primer pocket. Generally, I perform this inspection prior to annealing. It’s not terrible if you have 50 cases, but it sucks when you have 500 cases. It is for this reason I gravitate towards 12 grit walnut shell and not 24 grit.
Dust
Dry media is going to generate dust, it does not matter if it is walnut shell or corn cob, it is a byproduct of the process. This dust is something you don’t want to breathe in. It can contain lead, abrasives, and other unpleasant contaminants. If there is a good reason to add anything to walnut shell, a few teaspoons of mineral oil every so often will help to “wet” the mix and reduce dust substantially. The charging additives we put in corn cob media does this for us, but if you see that you corn cob media is getting dusty that is a good indication it is due for another charge.
Cheap media often is dustier from the get-go than more expensive media. This is where it is better to spend a few extra bucks to get something that is not the “bottom of the barrel”. It usually goes through a process that “cleans” the media of fine dust particles prior to bagging.
Cost
Dry tumbling costs more per batch than stainless steel media. Stainless Steel media will never wear out (in theory) and should last a lifetime of tumbling. Dry media needs to be replaced or recharged periodically. The upside is that we are not talking about a ton of money. $50 worth of dry media (10lbs of Corn Cob, 25lbs of Walnut media) will clean tens of thousands of cases before effectiveness drops off, especially if you do not subject the media to marathon tumbling sessions.
The upfront cost of dry tumbling is cheaper in most cases than the upfront cost of wet tumbling. In my opinion, wet tumbling is more time consuming, requires additional drying steps and does not polish the case, rather just cleans. So isn’t an apples-to-apples comparison.
Is this Better Than Wet Tumbling?
I honestly believe most guys start out with a vibratory tumbler purchase either walnut shell media or corn cob media and do not know how to use the different media effectively. Corn cob media, especially when it is untreated, will take hours of tumbling to get a good level of shine and may never get all the carbon out. Walnut shell media is better but will never get to show room quality, and again guys will tumble for long periods trying to get to it. I believe that is where the frustration happens, and then when wet tumbling came a long time everyone was thrilled by how clean the brass got with comparatively shorter tumbling times.
That must make it better, right? It is not that straightforward. Perhaps in a follow-up article we can poke that bear. In the meantime, I will leave you with the picture above. The 7.62×39 cases on the left spent 4hrs tumbling, 1st in untreated walnut media, and then a 2nd tumble after sizing in Lyman Treated corn cob media. The 300 Blackout cases on the right spent about 2hrs in a wet tumbler with stainless steel pins, 2+ hrs drying in a glorified food dehydrator with Alabama air and then were sized and spent another 1hr to wash of the lube, and another 2+hrs drying.
I ended up running the 300 Blackout cases back through the walnut media and then through the corn cob media. My OCD just couldn’t handle it.
Till next time,
Jay
I’m gonna keep using the wet wash. The results that I get with wet washing leaves my brass as clean as new unfired brass, inside and out. I used a dry tumbler for probably 20-25 years, and I’ll am about 99.9% positive that I’ll not use it again.
I knew there would be “bitter clingers”. I am joking, I personally think that everyone is going to use what fits in their process better. I do plan to do an article on Wet Tumbling, it has it’s merits and it does do a pretty dang good job of cleaning. I have just found for my space, and what I prefer I am happy with the try tumbler method.
I de-prime and wet tumble to clean and the last step is to polish with walnut shell dry media and NuFinish. Makes great looking shells and the NuFiinish prevents (doesn’t eliminate) finger prints from showing up later.
I make my own sizing lubricant with 10:1 99% (NOT 70%) Isopropyl alcohol and lanolin; a little bit goes a long way. Put it in a spray bottle and spray into a poly bag of brass, roll around, pour out into a container and let dry, then size. I’m still on my first bottle; it’s the best lubricant I found so far! It totally eliminated .223\5.56 stuck shells during sizing. And, it is unnecessary to clean it off if you don’t want to.
Hey Roger,
Thanks for the comment. I agree, a combine approach of wet tumbling for the initial cleaning, and then using a dry tumbling either in walnut shell or corn cob to give it a final polish is getting the best of both worlds.
I’ve messed around with making my own lubricant a few times, using the 99% Isopropyl with lanolin gives really good results, I’ve never stuck a case when using it. I’ve also messed around with adding 5% castor oil and 5% lanolin to isopropyl alcohol. The caster oil is supposedly a bit slicker but I never could tell the difference. While I have never had an issue with the alcohol and lanolin mix, I have just come to prefer a good sizing wax and have some pretty good success on whipping up my own from beeswax and lanolin. In the winter time it doubles as a balm for dry skin and cracked skin.