Hording firearms against civilization's collapse is not an approved reason to get a Federal Firearms License

See below for some context.

The Federal Firearms Licensing Center (FFLC) is responsible for determining eligibility and acting upon applications for Federal firearms licenses. Inspections of applicants are coordinated with regulatory field offices. Such applications are required to be filed by all persons who intend to engage in the business of manufacturing, importing, or dealing in firearms. Firearms licenses are also issued to persons who wish to be collectors of curio and relic firearms.

So, you could import them. Or rely on blunderbusses. Manufacturing? ... Man, you can get inspiration from anywhere.