How to Clean Cosmoline Off Your “New” Surplus Firearm

So you just bought a shiny new (to you) milsurp firearm, but the problem is that it’s caked in cosmoline, that nasty, waxy, smelly (and supremely effective) rust preventative that just about every military on the planet uses for long-term gun storage. What do you do to get that old gun in tip top fighting shape? It’s really simple!

I recently purchased a Finnish M39 Mosin rifle still packed in cosmoline and grease, which is a great excuse for me to document the process for the edification of my readers. To start with, you’ll need some things you probably already have unless this is your very first gun:

  • Whatever you need to disassemble the firearm, in this case a set of flat head non-tapered gunsmithing screwdrivers.
  • An oil with which to coat the metal parts; for me Rem-Oil is the height of cheap aerosol convenience, but almost any medium-weight oil will work.
  • A lubricant for the moving parts; I have a tube of TW25B that has lasted me several years so far and will last for many more.
  • Something to hold the gun parts. I will be using a 35″ plastic tub for the receiver components and a smaller plastic box for the smaller parts.
  • Mineral spirits or paint thinner (both are basically the same substance).
  • Plastic gloves, such as dishwashing gloves. I will be using disposable nitrile gloves.
  • A well-ventilated area.
  • A drying cloth.

I’ve had this tube of TW25B for… A while.

PHOTO_20160530_145548 PHOTO_20160530_133257


There wasn’t enough regular paint thinner available at the store, so I had to also buy “Safer Paint Thinner”, which was a milky color. I just mixed it with the regular kind, and it seemed to work fine.


Now, the actual process is about as simple as can be:

  1. Completely disassemble the firearm down to its smallest components. Do not take apart assemblies that were not intended to be disassembled, e.g. riveted components.


  2. Set aside any wood components of the firearm. If it is a sunny day, you can set the wood furniture out in the sun to help leech out the cosmoline that may be soaked into them. Do not leave the wood components outside for a long period of time unattended.
  3. Place the metallic components of the firearm into the containers, and take them to your ventilated area.
  4. Put on your gloves.
  5. Pour the paint thinner into the containers over the metallic components.

    PHOTO_20160530_150317 PHOTO_20160530_150332

  6. Wait for 15 minutes to an hour.
  7. Remove the gun parts from their containers. Make sure that any hollow components like oil bottles are thoroughly cleaned and drained.
  8. Wipe down all the components and apply oil to them; lubricate the moving parts as needed.


    After being wiped down and oiled.

  9. Drain the tubs into a container. Do NOT drain them into the sink or onto the ground! Paint thinner is a hazardous substance and must be disposed of properly.
  10. Reassemble the firearm.

Beyond that, simply put everything away and dispose of the used paint thinner as needed. Removing the cosmoline on a milsurp firearm is a great way to improve its function and appearance, and to eliminate “sweating” of the stock. Get that nasty crap off there, and enjoy your milsurps, folks!


My nice, cosmoline-free 1944 VKT M39!


Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • Dan

    According to their MSDS, the ordinary paint thinner is 95% Stoddard Solvent. So, if you can get Stoddard Solvent, white spirits, mineral turpentine, or Varsol, then you can use that as a paint thinner alternative. You can probably also use 99% isopropyl alcohol which is used as fuel in penny stoves.

    • M.M.D.C.

      Or odorless mineral spirits. Be careful about working with solvents without good ventilation.

      • Dan

        Alas, I work in the paint industry. Solvents smell sweet (especially the ketones) and once you get used to it, it just clears the sinuses! (Yes, it’s an Under Siege 2 reference.)

  • Jolly

    Using a heat gun on low temp melts most of the cosmoline away. Go over your wood parts several times with heat and a rag to release the grease from the wood grain.

  • politicsbyothermeans

    When I was working with the Iraqi army, they cleaned cosmoline off by dropping the entire rifle into a barrel of “benzene” and a spirited drive over bumpy roads or out in the desert. Not that I recommend that for a personally owned firearms, but it sure did the trick.

    • Nicks87

      No need to put much effort into it, Allah’s will helps the guns get clean.

      • politicsbyothermeans

        Funny you say that. The other two methods were to (mostly) unplug the barrel, put the giggle switch on “celebrate”, do two or three mag dumps and then shake the melted cosmoline off or to simply field strip the AK and leave the pieces out in the sun for about half an hour, wipe them down and reassemble.

        • Nicks87

          The Saudis I worked with would always say “Insha’Allah” when we talked about weapons cleaning. Basically meaning “if god wills it” so we always joked that Allah cleans their weapons for them.

    • Basil Sever Moulds

      Ahh good old benzene lol not OSHA approved

    • Frank

      That sounds so dakka

    • William M Butler, MSG USA ret

      Benzene is a word for gasoline over there.

      • politicsbyothermeans

        Roger that. It is definitely one of those words that never fails to make an Iraq vet smile, especially one who worked the early Iraqi Army. After Insha’ Allah, it was the next most common solution for most military problems, according to the jundi.

      • Archie Montgomery

        Yup. Gasoline works fairly well, but has attendant dangers.

  • DW

    Make garbage rods great again?

    • TxHawgHntr

      That took longer than I expected, guess Alex is busy today.

    • Alex Agius

      The m39s are much better than the mosins

  • PK

    Or, and I’m just throwing this out here as it’s much safer and cheaper, use Simple Green concentrate in place of the paint thinner or other solvent and keep the rest of the steps the same, but adding a rinse with water step after cleaning. Works great for me, and has for many years.

  • ozzallos .

    Or I’ve heard a quick trip to the local self serve car wash and the use of their power sprayer for a buck or two works wonders. But then I’m not looking to baby my surplus SKS either, so take that for what its worth.

  • Greek Preparedness

    Steam….Just steam…

    • Wanderlust

      Yep this. cheap steam gun is $30 or $15 on craigslist

    • Steve

      Even a heat gun on low will work wonders – look into how cosmoline is applied during storage and you’ll quickly understand how to remove it… just add heat; the same reason the stuff bleeds if you don’t clean it and go out shooting.

      I might try the mineral spirit route next time, but heating the parts/assemblies and cleaning with rags while wearing welders gloves has never let me down.

    • That’s the way I did mine. I didn’t want to use any chemicals because of my bad luck of getting them in my eye, and a steam gun worked nicely.

  • Captain Obvious

    Go chemical free. A 5 gallon bucket and a rack from an old stove or grill. Boil a couple gallons of water. Set the parts on the rack and the barrel/receiver and stock into the bucket. Pour the water over the parts. The water will melt and wash the cosmoline away and dry the metal. Probably have done a dozen rifles like that.

  • Pete Sheppard

    Back in the day, when whole military units were drawing weapons out of storage, they would boil the actions in barrels of water.

  • Klaus Von Schmitto

    This is what I’ve done to get the cosmoline stains out of the wood parts. Mix a paste of MEK (Methyl Ethyl Ketone) and whiting powder. Smear it over the worst places or the whole thing if you want. Give it an hour or 2 and then wipe it down with MEK soaked rags. Your stock comes out bright and grease free. Use some stock oil and you’re good to go. Use some reasonable safety gear with the MEK. Let the used MEK evaporate in the sun.

    • marathag

      If you have a pool filter, use the diatomaceous earth and the solvent.

      • Klaus Von Schmitto

        That’s a great idea. I do have a pool.

    • Charles

      rather than MEK I’d suggest acetone. You get about the same measure of solvent action with a good bit less chance of hurting yourself. MEK is VERY dangerous stuff, and will get past most any protective barrier available for the average worker.
      Once MEK gets through your gloves/apron/ect. it -WILL- permiate the skin and leave you quite sick. That’s all with no mention to what the vapours are capable of.

      I found that a ZEP green solvent /hot water mixture soaking followed by a quick rinse using steaming water takes care of the metals quite well.
      Scraping the majority of cosmo. with a wad of paper towels followed by several(many?) periods of the trash bag/hot sunny day tactic & further wiping with more -cheap- paper towels is going to clean the stocks good enough to finish that phase with clean t-shirt rags steeped in mineral spirits and more dry cheap paper towels which will be much less damaging to the long wood fibers and exposed end grains in the long run.

      • Klaus Von Schmitto

        Probably so. But, I worked with MEK and Trichlo 1,1,1 almost every day for 10 years and it didn’t seem to leave me pernamently danameged.

  • marathag

    Used to use a bucket of old diesel, back in the day.

  • Kirk Newsted

    You’re working way too hard. I tossed the small bits in a pot of hot water and the big bits got hot water poured over them. No paint thinner, no mineral spirits, no EPA mess to clean up.

    • I didn’t have to work very hard as it was. 🙂

      Hardest part was matching the eighteen different kinds of wood screws to their respective holes!

  • An alternate method is to make an easy bake oven out of a trash can and a 100W incandescent light bulb. Stripping the cosmoline from a ZB26 barrel’s fins if one of the worse cosmoline remove jobs I have ever encountered. I’m pretty sure the Czech military used it as a method of punishment.

    • Those are gunsmithing screwdrivers designed not to bugger up the screw slots. They have ground tips.

      Although whether my palsy-ridden hands will bugger them up or not regardless is another matter entirely…

      • John Yossarian

        So the in-the-white tips on those drivers have a hollow-grind? I was confused at first too, particularly because you said “non-tapered” in the article.

        I know Grace makes some good tools though – Their roll-pin punches have treated me very well.

        • “Hollow ground” refers to the curving shape of some screwdrivers that comes from the way they are ground. What’s important for gunsmithing purposes is that the tips have no taper and fit the slot precisely.

          The screws I have are not hollow ground; they aren’t made/shaped that way. However, they aren’t tapered either, and the tips are ground to precise dimensions, which is what’s important.

    • jay

      Nothing makes baby Jesus cry like seeing boogered up screw heads on guns! Love it!

  • Nobody Inparticular

    For the stock I’ve always wrapped it in a black garbage bag and set it in the sun.

  • Ed

    I always used break cleaner which dose the job very well. And pls Nathaniel do a run and gun with your M-39.

  • Todd G

    For Mosin barrels I use a commercial fluorescent light fixture cover/diffuser. 4′ long, about 5″ wide, and a few inches deep. The entire barrel drops right in. Also find purple power and similar grease cutting solutions work great. Cheaper and easier to work with than paint thinner.

    That’s the outside. Now, the inside of those barrels is a different story! Found a few tricks that can make the worst sewer pipe of a barrel shine. Sorta.

  • derpmaster

    Wimps. Gasoline and a scrub brush, followed by diethyl ether, followed by an overnight tetrachloroethylene soak.

    • Swarf

      No respirators. Smoking permitted.

      • MRHapla

        Ignite’em if ya got’em

      • Longhaired Redneck

        Correction: Smoking required!

        • derpmaster

          Lucky Strikes, unfiltered. Closed area for maximum effect. And you better be at least slightly drunk.

          • Longhaired Redneck

            “Hold my beer, watch this”…

  • What, you mean when I got a cosmo filled .32 acp for $15, it wasn’t proper to douse it in zippo fluid… set it ablaze, then pee out the fire, then try to see if this cleared the action/striker?

  • Kivaari

    For the metal parts only, try very hot soapy water. It melts the grease.

  • Goochylogic

    Lacquer thinner, the cure all for the metal and wood. Soak the stock first for an hour or so. After it dries I heat it up with a heat gun if no oil you are good to go. Then soak the metal parts then brush them. Good as new. Then oil properly.

  • Riley

    I toss the small parts in my ultrasonic cleaner. Clean the barreled action with simple green and clean the bore real good. The stock I wrap in paper towels, put it in a black garbage bag and put it in my truck in a warm day and it just swears out all the cosmoline.

    If there are any shims under the barrel mark it somehow and make sure they go back right where they were.

  • jerry young

    kerosene works well too, either way whether you use chemicals or hot water it is a messy job, heat will not remove all of it by itself, long ago when I was young one of the jobs I had was at a local auto dealer the cars would come in from overseas on ships, they had cosmoline on them, we used kerosene and good hot soapy water, this might not have been the best way but it worked

  • nova3930

    Cosmoline, Cosmoline, keeps your safe queen clean!

    • John

      I absolutely LOVE the smell of Cosmoline!

      And the smell of old WWII electronics coated with preservative!

      Someone should make a cologne with that scent!

      • CountryBoy

        “Eau de Bakelite”

      • Bill

        Yeah-and one that smells like the inside of old airplanes. These and Hoppe’s #9 should all be appropriately shaped air fresheners for your car!

  • jay

    I pulled my Enfield #4 MK1 apart, and lovingly cleaned every part with a brush and acetone. Then used easy off and baked the stock. After cleaning the stocks, steamed the teeth marks out of the stock, then lightly sanded the whole stock. Stained with a nice cherry wood stain, then tongue oil. Kept all the proof and serial number stamps, and everything is dated 1943. Have a 43 canvas cover and original sling as well. Next time I just might go the route in this article. As I’m not likely to be so in love with any other bolt or milsurp. Btw, I got reprimanded at 3 ranges for doing a mad minute run. SWEET!

  • Matt

    So, from Wikipedia, if you need to clean your mummy or firearm, use brake cleaner…

    “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.[citation needed]

    Cosmoline is also frequently applied to automotive disc brake rotors at the factory, to prevent corrosion inside the box before the rotor is placed into service on a vehicle. It is easily removed by spraying brake cleaner on the braking surfaces of the rotor.”

  • Drunk Possum

    Burnt Linseed oil for the stock after you sweat it. You’ll thank me for how amazing it looks when you’re done.

  • Rooftop Voter

    MEK, if you like dry alligator skin devoid of any body oils. Cracking and pain follow shortly if you do not have protective gloves. Learned the hard way after being tasked with cleaning armory Garands that had liberally coated with linseed oil all over the wood and metal parts. Previous LCDR thought it was a ‘good idea’ to preserve the rifles. Every action was gummed up, required dis-assembly/cleaning of 256 Garands to get them back into working order. Gtmo Bay, 1969.

  • Cmex

    Take it apart, wash the small enough parts in a bucket of paint thinner. Rub down the larger parts with a rag soaked in paint thinner. Soak patches in paint thinner and push them through the barrel. Then give the barrel, receiver, and action a good rubbing down with transmission fluid and then wipe off the excess with paper towels. All good to go.

  • AK1134

    i had cosmoline on my OLD AK magazines… Dropped them in the old dishwasher set it to high, 30 minutes later they came out nice and dry. While they were still warm and dry, I took some Frog lube to the out side and Hoppes to the inside wall and parts…. they work and look perfect still

  • Andrew Foss

    Wait for a hot, sunny day. Disassemble, wrap the stock tightly in a black trash bag with paper towels. put on your car’s dash. Glove up, Take your metal parts and drop into a metal bucket. Hit them with a can of brake cleaner (or make up a gallon of Ed’s Red: You don’t have to oil immediately after) and a toothbrush. Change gloves. Remove the stock from the bag and wipe with new paper towels. If you haven’t sweated out enough Cosmoline, replace the paper towels and stuff it back in the bag. If you live in a place that gets up to ~100, you can leave it standing outside with a paper towel under the butt end to wick more Cosmo out.

    This process worked on my Garand, its bayonet and my 91/30. YMMV.

  • Jamie Clemons

    I just wiped down my mosin with a little WD40 didn’t have any problems. A gun is supposed to be a little greasy it keeps the rust off.

  • That’s how I get Cosmolene off the metal.bits, that’s for sure.

    I managed to get my Poison Maggot stock Cosmo free using the oven cleaner method on the wood. If you do that the wood, there are a few *critical* tips:

    1. Remove *all* metal bits (screws, buttplate, etc.) before using oven cleaner and decontaminate the wood between oven cleaner applications with running water like you’re cleaning up after an NBC attack. Use a soft brush (like a paint brush) while flushing the wood with water.

    2. Air dry the wood (preferable out of direct sunlight, at least on hot days) thoroughly.

    3. You will now have a fuzzy, rifle stock shaped piece of grey driftwood. Use super fine sandpaper (or steel wool – I used finishing sanding sponges) to unfuzz it. Stain the wood with *oil based* stain (I found stain that exactly matched the original color). Defuzz it again, preferably with finer sandpaper or steel wool.

    4. Let air dry thoroughly.

    5. Apply your preferred protectant (try to get into the screw holes, etc.) , and reattach metal.bits. I used hand rubbed (wear gloves ) semi matte polyurethane, and it looks like it did when I had just rubbed the surface cosmolene off… only I can shoot it in the August sun in a while shirt, and not ruin the shirt.

  • Bill

    Don’t forget to make sure that the thinner won’t dissolve the tub, otherwise you’ll have a real mess on your hands. Ask me how I know this…

  • AirborneSoldier

    I simply put them in hot water in the shower. Cosmo melts off. If truly motivated, i then dissassemble, and use boiling water on stove. Rinse, put a fan over to dry, wipe it all down with light lube to prevent rust, re-assemble. Done. No chemicals to inhale.

  • Analogdino

    Years ago I got a “new in cosmoline” rifle. Stock off (to shorten it), I put it and the stock in the oven on “low” and most of it drained off (a couple of rotations help.) Then I wiped it all over carefully and re-oiled key parts. It worked perfectly for years, now sold.

  • Mike Lashewitz

    And to think I used paper towels Q tips and tooth picks to clean both of mine.