From the Scalia opinion in Heller:
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 in that way...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. (Scalia, page 8) . . .
Putting all of these textual operations together, we find that they guarantee the individual right to possess and carry weapons in the case of confrontation. This meaning is strongly confirmed by the historical background of the Second Amendment. WE look to this because it has always been understood that the Second Amendment, like the First and Fourth Amendments, codified a pre-existing right. The very text of the Second Amendment implicitly recognizes the pre-existence of this right and declares only that it "shall not be infringed." As we said in US v. Cruickshank..."this is not a right granted by the Constitution. Neither is it dependent in any manner upon that document for its existence. The Second Amendment declares that it shall not be infringed..."
Undoubtedly, some think the Second Amendment is outmoded in a society in where our standing army is thr pride of our nation, where well-trained police forces provide personal security, and where gun violence is a serious problem. That is perhaps debatable, but what is not debatable is that it is not the role of this Court to pronounce the Second Amendment extinct."