I agree that it is not a popular interpretation, and I will concede that they were probably not considering machine guns and WMDs when they drafted the document. But they were aware of the rapidly increasing rate of technological progress, and Dano is correct that the original intent of the Amendment was to prevent the state from becoming disproportionately more powerful than its citizens.
I know that most Americans would prefer a more moderate interpretation, and I can't pretend to know whether the Founding Fathers would word the Amendment the same way seeing our technological progress. But we have the Amendment that we were given, unless it is changed and ratified. I do believe that the way the 2nd is currently worded, any infringment whatsoever could potentially be struck down as unconstitutional. It's a fringe position in American society, which is ironic to me considering it merely follows the letter and intent of the Constitution.