The statutory language above is the very definition of “firearm” under the National Firearms Act, and it is the single sentence that places machineguns, short-barreled rifles, short-barreled shotguns, silencers, and destructive devices into a separate, heavily regulated class. Notice how the law does not merely list these items; it folds them into the broader term “firearm” so that any future restriction aimed at “firearms” can be stretched to cover them without new legislation. That linguistic sleight-of-hand is why ATF reinterpretations—whether on bump stocks, pistol braces, or forced-reset triggers—can instantly turn millions of lawfully owned items into contraband without Congress ever voting on the matter.

For the 2A community the implication is stark: the NFA’s architecture was built for prohibition, not regulation. Once an item is labeled a “firearm” under this section, every transfer, manufacture, or even possession becomes a potential felony unless the owner pays a tax, registers the item, and subjects himself to a web of federal oversight that the Supreme Court has never squarely held to be consistent with the Second Amendment. Recent cases such as Cargill and the Fifth Circuit’s brace ruling show courts beginning to question whether these categories can survive Bruen’s history-and-tradition test, yet the underlying definitional trap remains untouched. Until Congress repeals or the courts dismantle this foundational paragraph, every new accessory or innovation risks being swept into the same punitive framework that has criminalized common configurations for nearly a century.