That turns out not to be the case. Private ownership of cannon armed warships, was aknowledged in the main body of the Constitution, even before the second amendment was ratified, which provides Congress the power to issue letters of Marque. This ammounted to a "hunting license" for enemy shipping. The individuals didn't need the letter to own the cannon, nor the ships, nor to fit the ships with the cannon (although they did sometimes store the cannon until needed, when the ships were otherwise employed). Towns, more properly the militia of towns, and some indivduals did own artillery at the time. All are "arms" which the right of people to keep and bear is protected by the second amendment.