Defines the terms “firearm silencer” and “firearm muffler” in federal law to cover (1) devices made or redesigned to silence, muffle, or lessen the sound of a portable firearm that are intended to attach to a portable firearm, and (2) the outer tube or single component that houses internal sound‑reduction parts and attaches to a portable firearm. The change amends the statutory definition in 18 U.S.C. 921(a)(25), clarifying that both complete silencers/suppressors and single-piece outer housings used to hold sound‑reduction components fall within the legal definition.