Removing cosmoline from firearms
If you’ve ever been a collector of C&R guns, and really, why wouldn’t you want to be considering the convenience of having a C&R license, you undoubtedly have had your fingers and clothes covered in a viscous, sticky, disgusting layer of cosmoline, or a similar preservative.
It’s obvious why this was done. So much of this military surplus from around the world would be doomed to a short life of rust and rot if it had not been properly preserved. Sitting in cold, wet, dirty and often forgotten storage lends itself to deterioration of both metal and wood parts. Add to this the sheer scope of how much surplus is out there, and it makes sense that those doing the storage would want a way to quickly, cheaply and effectively store firearms for the long haul. Enter, cosmoline.
Wikipedia says of Cosmoline:
Cosmoline is the genericized trademark for a generic class of rust preventives, typically conforming to United States Military Standard MIL-C-11796C Class 3, that are a brown colored wax-like mass; have a slight fluorescence; and have a petroleum-like odor and taste (as detected when working with it).
Chemically, cosmoline is a homogeneous mixture of oily and waxy long-chain, non-polar hydrocarbons. It is always brown in color, but can differ in viscosity and shear strength. Cosmoline melts at 113–125 °F (45–52 °C) and has a flash point of 365 °F (185 °C).
Its most common use is in the storage and preservation of some firearms, hand tools, machine tools and their tooling, and marine equipment. Entire vehicles can be preserved with cosmoline. Notable Egyptologist Dr. Zahi Hawass recently disclosed that ancient Egyptian mummification practices from the third to fifth dynasties utilized a chemical compound molecularly similar to cosmoline.
During World War II, U.S. Coast Artillerymen (serving the huge coastal artillery batteries) were known as “Cosmoliners” because they were tasked with the near constant cosmoline application (“greasing down”) of the guns. Cosmoline was also used to coat weapons, including entire tanks, for long sea voyages, as it prevented rust even in salty conditions.
During Pacific island campaigns in World War II, the United States Marines sang a song about cosmoline. Adapting the popular big-band tune Tangerine they would sing “Cosmoline…keeps my rifle clean”.
Due to its gelatinous nature, cosmoline can be difficult to remove completely from firearms and, as such, is being extensively replaced with vacuum-pack PET film.
Over the years, I’ve tried everything to get this stuff off. All of these methods have some degree of success, but there’s really only two things that work every time: patience and elbow grease. Once you have both of those tools ready for the job, you’ll need the following:
- Mineral Spirits (1-2 gallons should be enough)
- 4″ PVC Tube (3 to 4 feet long). If you can find 6″ PVC pipe, even better.
- 4″ PVC Cap and screw-on cap. If you go with 6″ PVC pipe, go with 6″ caps.
- PVC Glue (I use the blue rain and dry stuff)
- Rifle Cleaning Rod
- Paper Towels
- Pipe Cleaners
- Bore Cleaning Oil
- Dawn Dish Soap
- Green Scrubby and Sponge
While I’ve done dozens of these cleanups over the years, I’m always amazed at how wildly variable the condition is. This SKS was one I just got in and it was thoroughly coated in the cosmo grease. I don’t think there was a single square inch of rifle, inside or out, that wasn’t slathered in it. I had a long job ahead of me.
Before cleaning, you’ll want to leave the gun outside in the sun for a few hours. This will cause the cosmo to loosen up and will aid the chemical bath that the rifle is about to go through. It also takes the texture of the coating from a hard sticky mass to a thinner more oily finish. Without this warm up procedure, the soaking in mineral spirits won’t be as effective.
While the rifle is soaking in the sun, this gives you time to build your soaking tube. Construct as shown below and secure to something that will hold the weight of the rifle and mineral spirits and tube, like a chair or flagpole or something similar. It’s best to do this outside, in case of spills and to allow the warmth of the sun to said in stripping. I constructed the tube with the bottom 4″ cap fitted with the rain or shine PVC glue. From here, I glued the screw-on fitting to the top and allowed it to cure for an hour.
I ended up building both a 4″ and a 6″ tube version. While I like the 6″ version so I can dump the whole rifle at once, it does take a lot more mineral spirits and the tube itself is way more expensive. While the 4″ cost me around $40 for the tube and spirits, I have about $130 into the 6″ version. Feel free to build whichever you like.
Once the PVC construction is complete and the glue has cured, pour mineral spirits into the tube to about 75%. Place the rifle into the tube, barrel down. Depending on the size of your rifle, it may go all the way down to the action. It may only cover the barrel. If you can get something larger than the 4″ PVC, it would likely hold the entire weapon submerged. That said, do what you can. We’ll be using elbow grease to finish the job, so don’t beat yourself up about what will and won’t fit into the tube.
Once the rifle has had 2 to 3 hours to soak, pull it from the pipe and take it to your washing area. I used my kitchen sink. You will be doing a lot of scrubbing here, so pick an area with lots of space and to spread out and lots of drain area so you can work the rifle clean in the most efficient way possible. You will note from the photo below that the miner spirits do a pretty good job stripping on their own. This photo is of the bayonet assembly post-dunk but before any additional hand cleaning was done. While it looks clean, there’s a long way to go.
You’ll notice that the wood itself had soaked up a lot of cosmo but the mineral spirits broke much of it free. Running your fingers over the wood will reveal a light greasy touch after the soak, with heavy cosmoline soiling still cramming into all of the nooks and crannies. While you can do a full disassembly of your rifle (which might make this easier), you don’t have to do a full field strip to do a thorough removal of the coating.
You can see the metal still has a dull finish to it after soaking. Obviously, it’s a lot cleaner than it was before the dunk, but this is no where near good enough to fire yet (or even store for that matter).
Now, we break out our friend Dawn. Dawn Ultra is the best soap I’ve found to do this job. You can probably do it with another soap but I’ve found Dawn to be the best at getting great out of both wood and steel and it creeps into the hard to reach spots.
With the buttstock of the rifle in the sink, soap up a green scrubby sponge and liberally apply the soap around the rifle. Work the bolt action back and forth, as well as the bayonet and the sights. As you scrub these surfaces, you’ll notice the white soap turning brown very quickly. Continually rinse with as hot of water as you can stand working with. Water in the 110 degree range (or hotter) combined with soap works wonders to get the broad surfaces clean without a lot of scrubbing.
Once the large areas are clean and you can handle the rifle without having greasy cosmoline left all over your hands, it’s time to work into the detail work. Looking at any moving parts, you’ll want to look at hinges and crevices and any place that might have cosmo packed into it. Note the fitting of the bayonet below. Even after cleaning it for more than 10 minutes, constantly working the part under hot water and reapplying soap time and time again, the grease seemed to be appearing from nowhere. This is a great place to use the Q-tips/cotton swabs, the wire brush and a tooth pick or precision tools to get into the tightest spots. This will take plenty of time and attention, so keep cleaning.
A look inside the bayonet storage slot shows that cosmo really creeps into everything. I let Dawn sit inside this channel for a few minutes before using a paper tower wrapped around a cleaning wire to make multiple passes through the trench. It took almost 15 minutes and dozens of paper towels to get this one part clean.
After several passes, I switched to a cotton swab and was still finding chunks of cosmo in the corners. You can see how this builds up on the tools so quickly. I went through around 200 cotton swabs in the process of cleaning his one rifle.
After thoroughly cleaning the bayonet, the rotating mount and the wood storage sleeve, the bayonet finally moved without cosmo squeezing out of everywhere. This is a good time, as you clean each area, to spray down (or wipe down) with a high quality gun oil. This will help preserve the finish and will remove any remaining soap and solvent. Always make sure you are drying each area with a paper towel as you work to prevent rusting and corrosion.
Working the bolt and cleaning out the bore took the most time. I’ve had to do this dozens of times and the bolt assembly, trigger, magazine well and inner barrel by far take the most time to clean. You may want to remove the bolt assembly all together and let it soak in mineral spirits by itself. You could leave it in the rifle while you clean, but that it may be more work in the end.
The magazine well on the SKS is especially prone to the cosmo being packed in. Not only is it a 3 piece assembly (spring, well, cap) but the the dipping process with the bolt closed leaves a thick wall of plaque that has no where to go. I find that I have to open this section all the way up, scrub vigorously with Dawn and a green scrubby under running hot water and then let it run under the hot water for 5 to 10 minutes. You may have to do a constant clean-rinse-dry-clean-rinse-dry cycle until the water runs clean and the inside isn’t greasy to the touch.
Did I mention that cosmo gets everywhere? This is a cotton swab from the inside of the bolt assembly *after* soaking the receiver in soap and water and after substantial cleaning. You will be finding bits of cosmo everywhere as you clean.
To give you an idea how much cosmo is likely packed into the action, this is what I pulled out with a cotton swab after 10 minutes of soap and rinsing inside of the magazine well. Chunks of the grease run along all the working parts and into the deepest crevices even after rinsing.
Once you think you have the outside and action of your rifle clean, think again. I had forgotten to flip up the rear latch after going over this a dozen times and there it was, packed with cosmo and waiting to be cleaned. I ended up soaking the back half of the rifle in hot soapy water after cleaning this and still had cosmo run off into the sink.
Now that the outside of the rifle is clean, it’s important to get the barrel completely clean. I started with a piece of paper towel folded up and pushed through the head of the cleaning rod, like this:
You will be amazed how much cosmo you push out. This is the first push. You can see that there is 2-3 tablespoons of cosmoline built up around the towel. Once pushed through, rinse the action from the bottom to the top in hot water and soap. You will rinse out most of what you knocked loose.
With a fresh towel, re-thread the cleaning rod and push again. Once again, a huge gob of cosmo will get pushed out. Repeat this process 8 to 10 times until the fresh paper towel runs clean and free of a greasy texture.
After all the working parts are cleaned out, always do one more bath in soapy water, top to bottom. By now, you should be at the 60 to 90 minute mark of scrubbing on this one rifle. If you’re lucky, your rifle won’t be this bad. I don’t see how it could be much worse. Regardless of how covered your rifle is in the sticky stuff, this tried and true method will work. It just takes time. Once clean, rub everything down with a high quality gun bore cleaner. I use Hoppe’s #9. It leaves everything shiny and smooth and lubricates while it cleans.
Now that you gun is clean and lubed, make sure it’s completely dry before storing. You may want to use a wood conditioner on your stock as well. Go enjoy your shiny new relic!