A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
As far as I can see, from both the plain meaning of the words and the writings of the founding fathers, the 2nd was originally meant to apply to all weapons from a dagger to a cannon.
The Heller decision (written by Justice Scalia) seems to be the prime originalist interpretation of the 2nd Amendment. However that case was primarily about restrictions on handguns, not about "arms" in general. It is the wider meaning of "arms" that iterests me here.
Heller quotes the following definiton of "arms":
Timothy Cunningham’s important 1771 legal dictionary defined “arms” as “any thing that a man wears for his defence, or takes into his hands, or useth in wrath to cast at or strike another.”
Given that a cannon is "used in wrath to strike at another" it certainly seems to fit the definition.
The other important term here is "bear arms". In the 18th century "bear" in this sense meant to carry, and this is the sense that Heller concentrates on. However the phrase "bear arms" more usually meant "participate in organised military action". Since organised military action at that time generally involved cannons it seems a big stretch to suppose that the framers intended to exclude cannons merely because they were too big for one man to carry. Also, at the time some cannons were in fact in private hands. In the War of 1812:
As soon as word of the war arrived, ship owners in the port cities up and down the Atlantic coast raced to get their sleek sloops and schooners to sea in their new predatory role. They found cannon where they could, signed up oversized civilian crews, and sent messengers to Washington to get licenses called letters-of-marque from the federal government.
The Heller decision also rejects the idea that the 2nd Amendment only applies to firearms that were commonly available at the time it was written.
So a plain reading of the 2nd Amendment seems to imply that every American (plus non-citizens in the USA) has a constitutional right to keep and bear any military weapon of any kind, including but not limited to heavy machine guns, fighter and bomber aircraft, bazookas, surface-to-air missiles and tanks. The right to ammunition for all of these is also covered by the term "arms", as the framers could not possibly have envisaged gunpowder and bullets being banned while guns being protected.
As I said above, Heller is mostly about handguns, but it does make a minor reference to heavier weapons:
Like most rights, the right secured by the Second Amendment is not unlimited. From Blackstone through the 19th-century cases, commentators and courts routinely explained that the right was not a right to keep and carry any weapon whatsoever in any manner whatsoever and for whatever purpose. [...] Although we do not undertake an exhaustive historical analysis today of the full scope of the Second Amendment, nothing in our opinion should be taken to cast doubt on longstanding prohibitions on the possession of firearms by felons and the mentally ill, or laws forbidding the carrying of firearms in sensitive places such as schools and government buildings, or laws imposing conditions and qualifications on the commercial sale of arms
Here Scalia stops analysing the original meaning of the 2nd Amendment, and instead depends on the 1935 Miller case. This seems very strange; not only is this a sudden departure from originalism, but the key holding of Miller was that
Only weapons that have a reasonable relationship to the effectiveness of a well-regulated militia under the Second Amendment are free from government regulation.
However the rest of Heller overturns this, finding that the 2nd Amendment also includes a right to personal self defence, and hence that non-military weapons (such as small calibre handguns) are protected. (A cynical interpretation would be that Scalia wanted to overturn the ban on handguns but not the one on on heavy weapons, and then reasoned backwards from his desired conclusion. However such speculation is outside the scope of Politics.SE).
I know the principle that "dangerous" or "unusual" weapons can be banned, but that makes no sense. All weapons are dangerous when pointed at you, and all new weapons are unusual when first invented. Also, if a weapon is banned then few people will have one, making this a circular definition.
One might reasonably construe "dangerous" as "having unpredictable effects", so for instance gas weapons and landmines could reasonably be considered unprotected. But any weapon used by the US military, with the possible exception of nukes, would fall outside this limitation.
Another attempt at restricting the 2nd is that arms are only protected for "lawful purposes". But again this fails the originalist test. The framers regarded the 2nd Amendment as safeguarding the right of "the militia", meaning all able-bodied men, to fight against invasion or tyranny. To this end they were also expected to practice using their weapons. So by an originalist reading of the 2nd Amendment, firing a bazooka at a firing range is a lawful and therefore protected activity.
Of course one might argue that if bazooka practice is made unlawful then bazooka ownership lacks lawful purpose and hence is unprotected. However the same argument could equally be made against handguns and combat knives; the argument basically renders the entire 2nd Amendment meaningless so it cannot be what the framers meant.
So my questions are:
Does an originalist reading of the 2nd Amendment support the right of any citizen to keep and bear heavy military weapons?
If so, do originalist interpreters of the US Constitution want to have a country where anyone can keep and bear heavy military weapons, or do they consider that the meaning of the 2nd should be understood in the context of modern technological civilization?
If the latter, then how do they distinguish their position from any other "living constitution" theory?
Or is there a third option I am missing?
(Note: a shorter version of this question was posted on the Volokh Conspiracy blog. It didn't get an answer there so I am posting it here.)