That's not what the militia means. The "militia" INCLUDED privateers, such that a member of the seaborne militia might own a fully gunned Man of War. That is, the second includes the right to own ALL armament.
But now, here is Heller. Happy pop-gunning.
Hundreds of thousands of AR-15 style weapons are made and sold here in the US every year. Very common. Used lawfully. The assault weapons ban will never be back.
Technically, that line *could* be interpreted to include cannon and warships. One cannot say that naval cannon were not in common use around the time of the founding by the citizenry.