Article I, Section 8 gives congress power to issue letters of Marque and Reprisal. The strong implication of this section is private ownership of warships, which include cannon, and potentially other crew-served weapons.
And, there is modern historical precedent which extends the power far beyond sailing vessels. In the early part of WWII, 1940s, a letter of Marque and Reprisal was issued to the Goodyear blimp to act as an anti-submarine asset off the west coast. While it was mostly spotting duty and the only weapon involved was a rifle, there is a modern precedent. And at a minimum there is an entire crew serving this aerial asset.
+1 good post