26 U.S.C. § 4182: Exemptions

The tax imposed by section 4181 shall not apply to any firearm on which the tax provided by section 5811 has been paid. For purposes of the preceding sentence, any firearm described in section 5811(a)(2) shall be deemed to be a firearm on which the tax provided by section 5811 has been paid. No firearms, pistols, revolvers, shells, and cartridges purchased with funds appropriated for the military department shall be subject to any tax imposed on the sale or transfer of such articles. The tax imposed by section 4181 shall not apply to any pistol, revolver, or firearm described in such section if manufactured, produced, or imported by a person who manufactures, produces, and imports less than an aggregate of 50 of such articles during the calendar year. All persons treated as a single employer for purposes of subsection (a) or (b) of section 52 shall be treated as one person for purposes of paragraph (1). Notwithstanding the provisions of sections 922(b)(5) and 923(g) of title 18, United States Code, no person holding a Federal license under chapter 44 of title 18, United States Code, shall be required to record the name, address, or other information about the purchaser of shotgun ammunition, ammunition suitable for use only in rifles generally available in commerce, or component parts for the aforesaid types of ammunition. The amendments made by this section [amending this section] shall apply to articles sold by the manufacturer, producer, or importer after September 30, 2005 . Nothing in the amendments made by this section shall be construed to create any inference with respect to the proper tax treatment of any sales before the effective date of such amendments.”