; firearm mufflers Section 4181 of such Code is amended by adding at the end the following: For purposes of this part, the terms firearm silencer and firearm muffler mean any device for silencing, muffling, or diminishing the report of a portable firearm. . (c) Conforming amendments (1) Section 4181 of such Code is amended by striking other than pistols and revolvers and inserting other than articles taxable at 10 percent under this section . (2) Section 4182(b) of such Code is amended by striking firearms, pistols, revolvers, shells, and cartridges and inserting articles described in section 4181 and . (3) Section 4182(c)(1) of such Code is amended by striking or firearm and inserting firearm, firearm silencer, or firearm muffler, . (d) Effective date The amendments made by this section shall apply to articles sold by the manufacturer, producer, or importer in any calendar quarter beginning more than 90 days after the date of the enactment of this Act. XVI Lawful purpose and self-defense 1601. Short title This Act may be cited as the Lawful Purpose and Self Defense Act . 1602. Elimination of authority to reclassify popular rifle ammunition as armor piercing ammunition Section 921(a)(17) of title 18, United States Code, is amended— (1) in subparagraph (B)(i), by striking may be used and inserting is designed and intended by the manufacturer or importer for use ; (2) in subparagraph (B)(ii), by inserting by the manufacturer or importer before for use