(ee) A functional grenade launcher. (vii) Any shotgun with a revolving cylinder. (viii) All belt-fed semiautomatic firearms, including TNW M2HB and FN M2495. (ix) Any combination of parts from which a firearm described in clauses (i) through (viii) can be assembled. (x) The frame or receiver of a rifle or shotgun described in clause (i), (ii), (iii), (vi), or (viii). (B) Certain firearms not included Such term does not include any firearm that is manually operated by bolt or lever action, or that is only capable of firing rimfire ammunition. . (b) Exemption from additional tax for articles acquired by the United States Section 4182 of such Code is amended by redesignating subsection (d) as subsection (e) and by inserting after subsection (c) the following new subsection: (d) Exemption from additional tax for articles acquired by the United States The tax imposed by section 4181(b) shall not apply to any article which is purchased by the United States or by a State or local government. . (c) Effective date The amendments made by this section shall apply to sales after the date of the enactment of this Act.