This legislation, titled the Banning Unlawful Machinegun Parts Act or BUMP Act, aims to prohibit devices and modifications that significantly increase the rate of fire of semiautomatic firearms or allow them to approximate the action of a machinegun. Specifically, it makes it unlawful to import, sell, manufacture, transfer, receive, or possess any device primarily designed to achieve these effects when attached to a semiautomatic firearm. The bill also prohibits devices or parts that eliminate the need for a separate trigger movement for each shot, thereby materially increasing the firearm's rate of fire. Furthermore, it bans semiautomatic firearms that have been modified in any way to achieve a materially increased rate of fire or approximate machinegun action. These prohibitions take effect 120 days after the bill's enactment. For semiautomatic firearms already modified in such a manner before the enactment date, owners must register them with the federal government within 120 days under the National Firearms Act. This registration allows for continued lawful possession and transfer of these specific firearms. The prohibitions do not apply to government entities or their authorized personnel.