; and (B) does not include— (i) a slide that partially or completely encloses the barrel; or (ii) an extension of the stock along the bottom of the barrel which does not encircle or substantially encircle the barrel. (39) The term detachable magazine means an ammunition feeding device that can be removed from a firearm without disassembly of the firearm action. (40) The term fixed magazine means an ammunition feeding device that is permanently fixed to the firearm in such a manner that it cannot be removed without disassembly of the firearm. (41) The term folding, telescoping, or detachable stock means a stock that folds, telescopes, detaches or otherwise operates to reduce the length, size, or any other dimension, or otherwise enhances the concealability, of a firearm. (42) The term forward grip means a grip located forward of the trigger that functions as a pistol grip. (43) The term rocket means any simple or complex tubelike device containing combustibles that on being ignited liberate gases whose action propels the tube through the air and has a propellant charge of not more than 4 ounces. (44) The term grenade launcher or rocket launcher means an attachment for use on a firearm that is designed to propel a grenade, rocket, or other similar destructive device. (45) The term pistol grip means, with respect to a shotgun or rifle, a pistol style grip, including a thumbhole stock or any other characteristic that can function as a pistol style grip. (46) The term threaded barrel means a feature or characteristic that is designed in such a manner to allow for the attachment of a device such as a firearm silencer or a flash suppressor. (47) The term belt-fed semiautomatic firearm means any repeating firearm that— (A) utilizes a portion of the energy of a firing cartridge to extract the fired cartridge case and chamber the next round; (B) requires a separate pull of the trigger to fire each cartridge