History and tradition would indicate that the people posess whatever firearms that are suitable for military duty.
When I carefully read the 2A, I conclude the not only do the people have the right to keep and bear arms, they also have the right to form themselves into militia groups and practice group tactics with those arms in order to best be able to defend their nation. Why else would we have a prefacing clause telling us that a well regulated militia is essential?
Of course the arms best suited to military use are protected.
Next read the body of the Constitution, in particular Article 1, Section 8, clause 11: "The Congress shall have Power To ...grant Letters of Marque and Reprisal..."
This clearly contemplates private ownership of crew-served weapons capable of taking on enemy shipping in time of war. Think about that for a few minutes. What you can own and practice with is limited only by your budget.