Jeez, you people can read the whole decision if you want to do so instead of simply shooting from the hip:

...Some have made the argument, bordering on the frivolous,
that only those arms in existence in the 18th century are protected by the Second Amendment. We do not interpret constitutional rights that way. Just as the First Amendment protects modern forms of communications, e.g., Reno v. American Civil Liberties Union, 521 U. S. 844, 849 (1997), and the Fourth Amendment applies to modern forms of search, e.g., Kyllo v. United States, 533 U. S. 27, 35–36 (2001), the Second Amendment extends, prima facie, to all instruments that constitute bearable arms, even those that were not in existence at the time of the founding.
                                 --DC v Heller, Opinion, p. 8