The external finish on a firearm enhances the appearance and provides protection. An effective surface finish, whether on metal or wood, preserves the value of the firearm and protects it from environmental damage.
Depending upon the gun design and the manufacturer’s workflow, cosmetic finishing may be applied before or after final fitting and assembly. Final cosmetic finishing is applied to the vast majority of guns before assembly.
Prior to the American Civil War (1861-1865), the standard metal finish for most military rifles and muskets was polished bare metal. Although polishing removed tooling marks, the surface was neither protected nor colored. As a result of a slow oxidation process, these firearms develop a brown surface called patina.
Starting with the 1873 U.S. Springfield, the U.S. military adopted commercial finishes. To enhance sales appeal, finishes are applied to commercial firearms. The most common metal finish in the industry is blued steel; the metal is chemically oxidized to produce a dark blue finish. Electroplating and anodizing are also routinely used methods for finishing firearms.