Registration is a measure I support, but not at the federal level. The 2A was intended as a limitation of the Federal government and vested the authority to regulate the citizen militias in the various states.
Of course, the modern interpretation of the 2A, as per the Heller decision, is that it provides for the protection of an individual right (self-protection) unrelated to the citizen militia, in much the same way that the Constitution is interpreted to protect a woman's right to privacy and, hence, to choose an abortion. And neither right is absolute; both are susceptible to reasonable regulation by the States.
Can such reasonable regulation include registration? Of course, as well as licensure and insurance.