Cleaning Corrosive Ammunition Residue - Part I
by Kirk Lawson

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The subject comes up from time to time, how do I clean the corrosive residue from my firearm after shooting corrosive (usually surplus) ammunition in it?

Why would you care? Well, some ammunition, particularly older surplus, is made with primers which contain corrosive metallic salts which attract moisture and promote rust and pitting in the barrel, chamber, and on the breach face. After shooting, it is important to clean the corrosive salts off before that happens. How quickly it could lead to damage is a function of environmental variables in your location. It could be quick and within a matter of hours, or it could be slow. Ambient humidity, temperature, and other local factors affect the speed of damage.

So what do you do about it? One common line of thought among shooters is that you need to neutralize the corrosive salts with something. However, many experienced shooters offer that the solution is not to "neutralize" anything, that it may not even be possible to "neutralize" metallic salts (in the traditional sense), and the actual solution is to "wash" the salts away.

The need to clean corrosive residues is actually older than many new shooters realize. Black Powder shooters know that traditional formulations of Black Powder leave residues as corrosive as spending time with a politician. They have been using various cleaning methods to remove corrosive residues and heavy powder fouling for a very, very long time.

Modern Black Powder cleaning methods include:

Cleaning with simple, cold water and (sometimes) soap. Scrubbing down the affected parts with cold water and a stiff bristle brush effectively washes away the corrosive salts. Some use a funnel and pour the water down the barrel or breach then bore brushes and patches. Follow that up with drying and a lubrication and preservative such as gun oil, bore butter, motor oil, mink oil, and/or olive oil. When soap is used, standard dish soap and Murphy's Oil Soap are both popular choices.

Cleaning with hot water and (sometimes) soap. The procedure is exactly the same as with cold water, but hot or even boiling water is used. The hotter the water, the quicker it will flash off as steam, leaving the metal parts dry with less possibility of rust-promoting moisture being trapped on the metal.

Cleaning with urine. No, you read that right. Urine. Urine contains ammonia and ammonia is known to be good at washing away or "neutralizing" corrosive salts. Before modern manufacturing processes, this was pretty much the only easy way to get ammonia. More on this later.

Many modern Black Powder shooters also like to use a home-brewed concoction referred to as "Moose Milk." Moose Milk is mixed from common and comparatively inexpensive household chemicals (well, most of them used to be common, anyhow). There are various recipes for Moose Milk available and, much like the home-brew "Ed's Red," if you don't feel like mixing it yourself from components, you can even buy it premixed. There are a great number of recipes, most include some common ingredients between them. I'll number them just to keep them separate.

Apparently the original Moose Milk recipe (#1) was
1 part Murphy's Oil Soap
1 part Hydrogen Peroxide
1 part Isopropyl Alcohol (91%) aka: 91% "Rubbing Alcohol"
(Some Black Powder shooters reject that this is actual "Moose Milk" and refer to it as simply an "old cleaning recipe but not Moose Milk.")

However, many Black Powder shooters have abandoned the use of Hydrogen Peroxide, likely because H2O2 is an oxidizer and mildly acidic in its own right.

Moose Milk recipe #2
2 oz. water soluble oil (this can be found at most machine shops)
2 oz. Hydrogen Peroxide
2 oz. Pine-Sol (tm)
16 oz. Distilled water
Some people also add 2 oz. of alcohol to their Moose Milk to keep it from freezing in cold weather.

Moose Milk recipe #3
Napa water soluble cutting oil (part number is 765-1526 for 1 pint)
Murphy's Oil Soap
1 liter water bottle
Rubbing alcohol (optional)
Fill water bottle half full with warm water. Add 2 oz. each of the water soluble oil and the Murphy's oil soap. Shake well to emulsify and it turns white.

Moose Milk recipe #4
1 oz. water soluble oil
20 oz. distilled water
2 oz. Murphy's Oil Soap
Shake well to emulsify.

Moose Milk recipe #5
Stumpy's Moose Milk
A general purpose blackpowder solvent and liquid patch lube. Shake well before using
3 oz. Castor Oil
1 oz. Murphy's Oil Soap
4 oz. Witch Hazel
8 oz. Isopropyl Alcohol (91%)
16 oz. distilled/non-chlorinated Water (non-chlorinated)

Smokeless Powder corrosive residue cleaning methods:

The most commonly recommended corrosive salts cleaner today is Window Cleaner with ammonia; commonly Windex (tm) brand. As has been noted, ammonia is good at washing away and "neutralizing" corrosive salts. Window cleaners, particularly generic brands, are inexpensive and come in their own spray bottle. What's not to like? Well, one possible catch is that the percentage of ammonia in window cleaners is fairly low. Even Windex (tm) has only about 5% ammonia. The method used to clean (pre-clean, really) varies from person to person. The two most common methods are 1) spray cleaner down the breach end and let it run out the muzzle end, and spray on the breach face, then use patches to wipe off the cleaner and run a patch down the barrel 2) spray cleaner on patches and run through the barrel & wipe down the breach face, feed ramp, etc.; usually 2-4 patches. This removes/neutralizes the salts but does not otherwise clean, lubricate, or protect the metal. A standard cleaning and lubing will need to be performed on the firearm.

Another, somewhat less common, ammonia formula supposedly comes from WWI. A simple mix of one-to-one household ammonia and water. 1 part ammonia, 1 part water. Use same as window cleaner. This is part of what's troubling about the window cleaner option. In this, supposedly historic formula, it is a 50% ammonia solution. That's 10 times greater than the window cleaner ammonia content. Does the window cleaner have too little ammonia? Did the WWI gun smiths mix it more concentrated than they needed to for some reason? Was it just simpler to use a 50/50 mix at the time? I have not been able to find the answer to this question yet but it is intriguing.

Some shooters use a commercial product called Ballistol. Ballistol was formulated at the request of the German government prior to WWI and was in use up to the end of WWII. Formulated during the height of corrosively primed ammunition, it is intended as a CLP (Clean, Lubricate, Protect) firearm product and needed to be able to effectively clean corrosive salt as well as CLP general smokeless residues and clean & condition wood furniture on the firearm. Think of it as an early equivalent of Breakfree CLP (tm) which had to also clean corrosive salts and condition wood stocks. The manufacturer also advertises that the product is "green" ; i.e., it is non-toxic and environmentally friendly. The main ingredients are apparently Mineral Oil/White Oil, Oleic acids ("fatty acid" plant extracts), and alcohol. The product is emulsified in water where it forms a white creamy liquid, depending upon the ratio of Ballistol to water mixed (the manufacturer recommends different ratios for different applications). When used to simply wash away or "neutralize" corrosive salts, the process is much the same as for the ammonia concoctions: wipe down the areas with a few passes of wet patches. This has the added advantage of also being much the same as the cleaning process used with the product.

Finally, some shooters don't do anything special at all to clean corrosive salts from their firearms. They simply clean their firearm as they would any other shot with non-corrosive primers. They just make sure to do it in a timely manner before any rust or pitting can begin. If you are going directly home after shooting corrosive ammunition and will clean immediately, then there is unlikely to be any problem. If, on the other hand, you are planning an all-day shooting even and/or don't plan on cleaning the firearm until the next day or later, then certainly treat your firearm for corrosive salts as soon as it cools enough to do so.