Is a license needed to engage in the business of engraving, customizing, refinishing or repairing firearms?

Yes. A person conducting such activities as a business is considered to be a gunsmith within the definition of a dealer.

[18 U.S.C. 921(a)(11) and (21); 27 CFR 478.11]

Source: 

“Bureau of Alcohol, Tobacco, Firearms and Explosives.” Is a License Needed to Engage in the Business of Engraving, Customizing, Refinishing or Repairing Firearms? | Bureau of Alcohol, Tobacco, Firearms and Explosives, www.atf.gov/firearms/qa/license-needed-engage-business-engraving-customizing-refinishing-or-repairing-firearms.

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