FR.13

"Parts" specifically designed for a "firearm" and essential to its operation, including a barrel, frame or receiver, slide or cylinder, bolt or breech block, and any device designed or adapted to diminish the sound caused by firing a "firearm". Any "essential component" of such "firearms": the breech-closing mechanism, the chamber and the barrel of a firearm which, being separate objects, are included in the category of the "firearms" on which they are or are intended to be mounted