But compare the language of the first amendment "Congress shall make no laws" vs. the second: "shall not be infringed". There is no limit to the infringing agency in the second.
Also, look at the Congressional power to grant letters of mark and reprisal. This is the authority Congress can grant to private citizens to make war against the country's enemies. To do this required cannons and Congress wasn't passing those out, which implies the private ownership of the 18th Century's weapon of mass destruction and not merely muskets.
mark -> marque