Cosmoline is very similar to Vaseline. It was used as a preservative for firearms during WWI and WWII before the guns were put in storage. The guns would be dipped in a large barrel of Cosmoline to keep them from rusting. The Cosmoline did its job in preserving the firearms but left some sticky, messy guns behind. Knowing the best ways to remove Cosmoline can have your old guns looking like new again.
Take the Gun Apart
Since the gun was dipped in a large vat of Cosmoline, the ointment will be all over most of the gun parts. To reach the Cosmoline in the interior of the gun, you will need to remove the stock and remove the receiver and barrel from the stock. Then remove the bolt carrier and bolt, the recoil spring and guide, the trigger grouping and the operating rod.
Heat the Cosmoline
One method used to remove Cosmoline is to put the gun in the oven and melt the Cosmoline. It will become more of a liquid than a paste and will eventually dissolve. Place a tray covered with tinfoil on the bottom oven rack and turn the heat setting to warm. Put the stock in the oven for 20 minutes. Then remove the gun and wipe it down with a soft cloth.
Use Paint Thinner
Using paint thinner is one of the best ways to remove Cosmoline. Place the paint thinner in a pan that allows you enough room to work with the gun parts, and use a small paint brush to thoroughly wash each part with the paint thinner. It will not take long for the pan of paint thinner to become filled with Cosmoline. When it gets too filthy, dump it out and pour in a fresh supply of paint thinner.
Use an Air Compressor
Blow the remaining Cosmoline off of the gun parts with a air compressor. Keep working on each part until all the Cosmoline is gone. Use a toothbrush to get into smaller nooks and crannies on the bolt and other small areas of the gun. The sight assembly is probably caked with Cosmoline and may take extra effort to get it clean.
Clean the Stock
After you have cleaned all the interior parts of the gun, clean the stock. Use scrubbing pads to remove the Cosmoline. Then wipe the gun dry and set it near a fan for an hour or until it is completely dry and ready to be refinished. Lightly sand the stock with a medium-grade sandpaper. Then it is ready to be stained. It is not necessary to bleed the oil in the stock. Put the gun back together in the reverse order you took it apart.