Actually, there's some solid documentation that the Founders envisioned people having a lot more than flintlocks.
In the U.S. Constitution, Article 1, Section 8, lists, among the other powers of Congress, the power to " . . . grant Letters of Marque and Reprisal, and make Rules concerning Captures on Land and Water;"
Letters of Marque in the 18th century were intended to legitimize privateers to act in a warlike manner against a government's enemies; in other words, the Founders envisioned and allowed for private ownership and operation of warships on the high seas! Much more than mere muskets . . .
Perhaps this should be revisited if and when the question of how to deal with pirates in places regular navies aren't interested in intervening. (e.g., offshore from Somalia.)
That's an EXCEPTIONALLY dangerous position to take, and not one that you, I, or anyone else wants to run with.
If Congress has the authority to grant, or NOT TO GRANT, letters of marque, well it just goes to reason that they also have the authority to grant, or NOT TO GRANT, firearms rights under the Second Amendment.
After all, letters of marque were included in the main body of the Constitution, they weren't an obvious afterthought...
And, given the fact that letters of marque haven't been granted since the 1856 Paris Declaration, well, Congress isn't interested in issuing you any Second Amendment rights, either.