First, a "living" constitution is as desirable as a "living" sales contract. Think about it.
Second, the Second Amendment does not address firearms, it addresses arms, which may or may not be firearms.
What is a firearm? It is a device which propels an object by means of expanding gas formed by an explosion, usually gunpowder or its modern day variants.
There is no cut-off. My wants, desires and needs are not for you to restrict.