Some info
Gun Control Legislation and Homemade Guns
The federal Gun Control Act of 1968 (GCA) requires, among other things, that persons "engaged in the business" of dealing in firearms be licensed by the federal government. This law made it illegal for an unlicensed person to make a firearm for sale or distribution.
A non-licensed person may make a firearm, provided it's not for sale and the maker is not otherwise prohibited from possessing firearms. (18 U.S.C. § 922 (d) (2022).) Federal law imposes none of the purchase restrictions on non-licensed possessors that it does on those who need licenses, and as a result, the homemade gun owner need not undergo a background check, and the gun doesn't have to be registered unless a state law requires registration.
state governments and local municipalities (cities, towns, and unincorporated areas) can regulate them as long as the regulations don't conflict with federal law.