The words of the Constitution are there to convey ideas and concepts, as they were understood by the Founders at the time the document was written. While there is a case to be made that the 2A doesn't apply to the States, I find the assertion that the Founders would not consider a modern firearm to fall within their understanding of the concept of "arms" ludicrous.
They didn't have car bombs in 1791 either. Should I assume then that I have a constitutional right to drive a car loaded with C-4? Do I have a constitutional right to own a howitzer or a Sherman tank and haul it around the city?