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Barrel leading is a progressive condition caused by firing lead bullets through a gun barrel. Gunpowder explosions generate temperatures of about 5,000 degrees Fahrenheit. Lead melts at only 621.5 F degrees and boils at 3,180 F. For a shooter, the result is each time a lead bullet is pushed down a barrel bore it leaves a thin residue of lead behind. Over time with the firing of many shots enough lead is deposited so as to both reduce accuracy and also to hamper the passage of more bullets (which can cause variations in both pressure and velocity).
{A similar problem exists for copper jacketed bullets, but for copper the problem is more easily resolved. Further the melting point of copper, 1,984 F, ia high enough so that comparatively little copper is left behind given the short duration of the bullet’s time in a gun barrel.]
Early muzzle loading and black powder cartridge weapons were often made of simple iron or early steels which can not withstand the pressure spikes of smokeless powders. Generally speaking adding a copper jacket to a lead bullet dramatically increases pressures. If your weapon is barely strong enough to withstand the pressure of a gun powder charge with a lead bullet, replacing the lead bullet with a copper clad projectile is not the wisest of moves. Therefore shooters of antiques and muzzle loaders are restricted to lead bullets and black powder (and safe BP substitutes).
An additional complication is the often encountered presence of was or other lubricants being added to the bullet’s surface. Most shooters who shoot black powder weapons are aware that black powder combustion produces a mix of carbon, sulfuric acid vapor, nitric acid vapor, water vapor, and various other compounds which if left and not promptly removed from a gun barrel will inevitably lead to corrosion, pitting and rust.
The normal cleaning of black powder residue involves hot soapy water, and much scrubbing with clean dry patches, followed by an application of a light coat of oil to prevent the steel oxidizing (rusting) further. Some shooters also use watery solutions of ammonia or baking soda to neutralize any leftover acids in the bore early in the cleaning process.
Some shooters, after removal of the sludge accompanying black powder firing attempt to remove the lead using such commercial formulations as Hoppes #9, or Outers gun cleaner solutions. Usually the primary effective ingredient in those formulations is a denatured ether. This will dissolve copper and even steel, but it has no effect at all on lead, so such efforts to remove lead with those formulations are fruitless and useless.
None of these methods remove the melted lead which has adhered to the barrel steel. There are only 3 known methods of removing a build up of lead from a gun barrel.
The best method is electrolysis with a carefully designed mix of certain specific chemicals. If the voltage and the chemical mixture is precise, only the lead will be removed from the gun barrel and the steel will be untouched.
A popular method is to wrap a bore brush with a copper mesh product, such as copper from a “Chore Boy” scrub pad, then scrub and scrub until the lead is gone. Not a perfect method, but it does remove some of the lead. It is based on the copper being softer than the steel or iron of the gun barrel, but harder than the lead coating the barrel. In theory the copper will scrape out all the lead. Sometimes this does work. Sometimes not.
A third method is the chemical removal of lead. In this process a chemical that dissolves lead is introduced into the gun barrel. If the chemical mixture is correct the steel of the gun barrel will be unharmed when the mixture is poured out taking the removed lead with it.
Historically in the early 20th century one chemical mixture used by old time gun smiths to remove lead from a barrel was a 50/50 mix of 3% Hydrogen Perozide and White vinegar. Old gunsmith writings caution the mixture must not stay in the barrel onger than 20 minutes or else damage to the steel of the gun barrel may result.
Being curious I decided to test the effectiveness of the mixture. Here is a 23 minute video of the test. The results may surprise you.
There may be other mixtures known to some, if you are a chemist and know of one using readily available components, feel free to post it. Likewise if someone here actually knows what causes the strange effect shown in the video, please feel free to comment about it.
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