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Bluing, a type of metal finish common to older firearms, can wear off over time. Some gun owners choose to re-apply this coating, which is called “rebluing.”
Depending on the type of rebluing that you intend to perform, this may be more or less complicated. However, by adhering to a few simple instructions, you can restore your rifle’s finish to what it used to be.
What is Bluing?
Bluing is a passivation process whereby the steel generates a black iron oxide layer on the surface that acts as a protective barrier against the rust. Named for its blue-black color, bluing is a classic firearm surface finish treatment that gunsmiths and firearms manufacturers have employed for hundreds of years. Although uncommon on military firearms, the bluing process is still used on civilian sporting AR-10 rifles and revolvers.
Bluing, however, can wear off over time. If you’ve ever been in the market for a used handgun, you may have seen telltale signs of holster wear — the bluing having rubbed off the slide and frame where it contacted the leather. Bluing is particularly susceptible to this kind of wear. As a result, some gun owners choose to reblue the metal parts showing signs of wear.
However, while considered cosmetically attractive by many shooters, bluing is not as strong as other coatings/surface treatments.
Bluing vs. Other Treatments
As a surface treatment for resisting rust, bluing is one of the least effective options available. More decorative than anything, the black oxide layer that forms on the surface offers limited abrasion resistance and is susceptible to pitting, which is why it’s necessary to periodically wipe the barrel and other metal surfaces clean.
If you live in a cold or humid environment, you should also consider applying a few drops of oil to the barrel, receiver, and other blued metal parts with a lint-free cleaning cloth.
In comparison, zinc and manganese phosphating (parkerizing), a type of coating developed later in the history of firearms, offers increased wear and corrosion resistance. However, parkerizing doesn’t provide the same highly polished or deep blue-black finish that some firearms enthusiasts and collectors desire. It’s more of a matte black or dark grey finish that can fade over time. As a functional coating, parkerizing is highly effective, which is why it’s so common on military firearms, both old and modern.
Chrome and electroless nickel plating offer increased wear and corrosion resistance while also providing a decorative finish. However, these are relatively expensive and can be brightly reflective.
A modern surface treatment is ferritic nitrocarburizing, which penetrates the surface of the metal and significantly increases corrosion and wear resistance compared with bluing and parkerizing.
How to Reblue Your Rifle
When learning how to reblue a rifle, it’s important to note there are several different types of bluing processes for firearms. The first and perhaps most well-known type of bluing is hot bluing. If you want to hot-blue your firearm, you’ll first need to disassemble and clean the firearm.
Remove any springs or pins that you don’t want blued. You should then remove all traces of bluing or other finish material from the steel surfaces, rust or pitting, and any uneven surfaces or wear. You can use a type of high-grit sandpaper to perform this polishing work.
The hot-bluing or caustic black solution consists of a salt mixture of potassium nitrate, sodium hydroxide, and water. You’ll raise the temperature of this salt mixture to a temperature between 275 and 310°F.
Lay all gun parts you wish to blue in the salt mixture for between 15 and 30 minutes. Periodically check to ensure the parts are taking on the kind of color you want. When they achieve the particular tone you’re seeking; you can remove them from the bluing solution.
The next step is rinsing. You should rinse all blued parts first in cold water to remove any excess bluing solution. Leave the parts to air dry for a few minutes.
Once the parts have dried, submerge them in boiling water for 15–20 minutes. More complex parts may need to boil for a longer duration to remove any remaining bluing.
Soak the blued parts in an oil bath to further protect them from corrosion.
Another type of bluing that you can perform is cold bluing, which doesn’t require a heat source. You should use high-grit sandpaper, 320 and 600, to remove any remaining finish and rust that may have accumulated on the surface. Steel wool can help with the buffing process between coats.
Unlike hot bluing, you’ll be applying the cold blue solution to various parts of the gun’s surface using cotton swabs or gun cleaning patches. Cotton swabs allow you to apply the solution to small parts and close-tolerance spaces between articulating surfaces.
For degreasing gun parts, consider using a fast-drying solvent for either hot or cold bluing, such as acetone. However, be warned that acetone emits fumes and can destroy rubber and nitrile gloves, so proceed cautiously. As with any cleaning procedure or working with potentially toxic chemicals, you should prepare these parts in a well-ventilated environment.
For cold bluing, because there’s no submersion required, you should have a way of securing gun parts without damaging them. A bench vice is a superb way of holding parts in place for cold bluing; however, steel vice jaws can easily mark the finish or damage the metal. As a result, you should invest in a pair of rubberized jaws or plastic vice blocks.
You should plug the muzzle and breech to avoid cold-bluing solution entering the barrel from either end. While a hot-blue finish on the inside of the gun’s barrel is customary, cold bluing is more for touch-ups.
When bluing gun parts, you’ll be working with highly caustic chemicals. Always wear rubber gloves and any other appropriate personal protective equipment (PPE). Ideally, you should also work in a well-ventilated environment and keep bluing chemicals, cleaning solvents, and other products away from open flames or heat sources.
Before you ask how to reblue your rifle, you sure first ask, “Should I?” You should ensure that you’re not potentially compromising the collector’s value of a rare gun. If a collectible rifle like AR-15, for example, has 85% of its original blued finish intact, stripping the original finish and rebluing it will not add to its market value. You may be reducing its resale value.
If you’re interested in bluing a firearm for the first time, you should also determine whether this is the most cost-effective option. For older firearms, bluing complements the style and design of bolt-action sporting rifles, single- and double-action revolvers, and some non-military semi-automatic pistols beautifully. However, if you’re less interested in cosmetics and more interested in practical coatings, there are more effective options on the market.
Bluing is a surface finishing treatment that’s appropriate for specific styles and designs of firearms. As a rust-preventative coating, bluing is the least effective but offers cosmetic flair. As bluing fades or is worn away from use, you may decide to reblue the surface, restoring that blue-black luster. Rebluing is relatively simple, depending on the type, if you follow a few simple guidelines.
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