The following tutorial will show you around the part 479 landing page.
27 CFR Part 447
Importation of Arms, Ammunition and Implements of War
27 CFR Part 478
Commerce in Firearms and Ammunition
27 CFR Part 479
Machine Guns, Destructive Devices, and Certain Other Firearms
27 CFR Part 555
Commerce in Explosives
27 CFR Part 646
Contraband Cigarettes
27 CFR Part 771
Rules of Practice in Explosive License and Permit Proceedings
Effective date is the date this part was last amended
A firearm may be made by, or on behalf of, the United States or any department, independent establishment, or agency thereof without payment of the making tax. However, if a firearm is to be made on behalf of the United States, the maker must file an application, in duplicate, on Form 1 (Firearms) and obtain the approval of the Director in the manner prescribed in § 479.62.