; and (B) does not include an attached tubular device designed to accept, and capable of operating only with, .22 caliber rimfire ammunition. . (b) Related definitions Section 921(a) of title 18, United States Code, as amended by this Act, is amended by adding at the end the following: (38) The term barrel shroud — (A) means a shroud that is attached to, or partially or completely encircles, the barrel of a firearm so that the shroud protects the user of the firearm from heat generated by the barrel; and (B) does not include— (i) a slide that partially or completely encloses the barrel