I don't believe the piece of paper you're referring to explicitly guarantees personal firearm ownership as a right, actually. Same isn't the case with voting which is pretty explicitly spelled out.
And it's immaterial either way since one has to do with one's representation in government which is actually an organic necessity in a functional democracy, the other has to do with being able to stop the federal government from taking your slaves away -- sorry, I mean... unrestricted public weapons ownership, which is actually not necessary for a functional democracy and can be argued is a sign of a failed state.