Copper solvent is a chemical solution used for removing copper residue from the barrel of a firearm. It is sold commercially for use in cleaning hunting rifles. While many copper solvents incorporate ammonia, which can be used to dissolve copper residue, some products are made with minimal to no ammonia in order to protect the interior metal of the barrel from chemical etching.
When rounds are fired from a rifle, copper residue from the bullets is left behind in the barrel and accumulates over time, resulting in copper fouling. Copper builds up on the interior of the rifle bore — the hollow cylinder through which the bullet passes — and eventually begins to abrade and score the bullets as they are fired. The damaged bullets are aerodynamically flawed and cannot fly straight, compromising the rifle’s accuracy. Periodic cleaning of the rifle barrel with a copper solvent is necessary to eliminate fouling and preserve the rifle’s ability to shoot accurately.
Ammonia can be used to break down copper residue, although typical household ammonia-based products are not concentrated enough to thoroughly clean the bore. A solution of at least 10% ammonia is necessary. Many commercial copper solvents use ammonia as the main cleaning agent.
While ammonia-based copper solvents are usually formulated in such a way as to prevent or minimize potential damage, there is sometimes concern that the ammonia will corrode the interior metal of the gun barrel as it removes the copper fouling. For this reason, many companies offer “ammonia-free” copper solvents. These solutions work using different chemical principles. For example, a non-ammonia copper solvent might work by removing electrons from copper metal atoms, or oxidizing them, and then binding to and removing the oxidized product.
Solvent products are used in different ways depending on their design, but the basic cleaning procedure is roughly the same. A patch is wet with the copper solvent and pushed through the bore. This step may be repeated a few times, followed by brushing with the solvent using a nylon brush. The barrel may then be soaked for a few minutes and dried by running several dry patches through it. A small amount of solvent may be reapplied before the firearm is stored, although it is recommended that the amount be light in order to prevent residue from forming.
Some rifle owners choose to make their own copper solvents using industrial-grade concentrated ammonia or other chemical solvents, such as acetone. This approach has the benefit of being less costly than purchasing ready-made copper solvents. Since creating a copper solvent involves mixing potentially hazardous chemicals, however, most recipes recommend that precautions such as eye protection and ventilation be observed and that the official Material Safety Data Sheets (MSDS) containing information about the chemicals be kept on hand during the process.