Holding an FFL to engage in certain such activities has been a legal requirement within the United States since the enactment of the Gun Control Act of 1968.
[5] In addition to a current FFL (of whatever "type" is applicable), the ATF requires that business owners who are planning to import, manufacture or deal in restricted materials also pay a Special Occupational Tax, or "SOT" (thereby making the business owner a "Special Occupational Taxpayer").
(D) At the election of a licensed collector, the annual inspection of records and inventory permitted under this paragraph shall be performed at the office of the Attorney General designed for such inspections which is located in closest proximity to the premises where the inventory and records of such licensed collector are maintained.
An example would be a Lee–Enfield or 98K Mauser military rifle that had been converted into a continental style sporter before World War II.
Federal law defines guns manufactured in or before 1898 with unconventional firing mechanisms (such as percussion, flintlock and other combustion methods typically considered "black powder"), or cartridge firearms that have uncommon and not readily available ammo types (.30-40 Krag, .30 Mauser, .44 Russian, etc) as "antique"[8] (26 USC §5845(G)), (27 CFR §478.11) and they are generally unregulated in federal law.
The only exceptions are short-barreled rifles, short barreled shotguns, and machine guns, which are regulated under the National Firearms Act of 1934.
[10] Licensed dealers must also maintain file copies of Form 4473 or eForm 4473 "Firearms Transaction Record" documents, for a period of not less than 20 years after the date of sale or disposition.
[13] International Traffic in Arms Regulations (ITAR) is a set of United States government regulations that control the manufacture, export, import, or transfer of defense-related articles and services on the United States Munitions List (USML), which includes most all firearms components.
In general, the Department of State's Directorate of Defense Trade Controls (DDTC), which interprets and enforces ITAR, requires anyone engaged in such activities, including holders of a federal firearms license, to register annually and submit a fee (no less than $2,250 as of 2013).