But personal ownership of firearms was an unquestioned right at that time, covered properly by Article IX Concerning Rights not Enumerated.
The Second Amendment went BEYOND this ( literally ) unquestioned right, and affirmed the right of states to support their own militias.
So I would deny that it has "nothing to do" with the private ownership of firearms.
The chief author of the 2nd clearly defined what the militia was in the federalist papers
“the militia is every person in this country. We are the militia”
You're going to have to explain that one a little more...