Maintaining, repairing, modifying, and customizing firearms falls under the purview of the craft or profession known as "gunsmithing." Professional gunsmiths have comprehensive knowledge of firearms and their components due to their intensive training.
Even historical or antique firearms are repaired and modified by gunsmiths. They are adept at disassembling and reassembling weapons, diagnosing mechanical issues, replacing or repairing damaged parts, installing customized additions, and restoring or polishing the exterior.
Gunsmithing calls for mechanical aptitude, a comprehension of firearms' construction and operation, and practice with a variety of specialized tools and machinery. In the course of their labor, a gunsmith's knowledge of ballistics and ammunition, as well as gun laws and regulations, could be beneficial.
Despite the fact that many gunsmiths find employment in retail gun stores or manufacturing facilities, others opt to go it alone. Due to the intricacy involved, some gunsmiths specialize in engraving, stock fabrication, or barrel fitting rather than general gunsmithing.
Because gunsmiths work with live ammunition and other potentially lethal weapons, they are required to prioritize safety and comply with all applicable laws and regulations.

Guide on Gunsmithing: Beginners Guide To The Tools, Techniques, And Traditions Of Gunsmithing