
Alright, I'll bite: Historically, the second Amendment was meant to to refer to guns being allowed inside of a well-regulated militia. This is accomplished by the states' National Guards. It was not intended to mean that each person gets to have a gun.
This, according to America's Constitution: A Biography by Akhail Reed Amar. Great read, it walks the reader in a novel-type way through each part of the Constitution.
But, we've expanded the 'meaning' of the Constitution several times in ways the founders would have never anticipated. This in like with the 'living document' aspect, and a direct result of our veneration of document that is quite short.