The idea that state-by-state (or, just as likely, county-by-county) gun regulations couldn't work flies against reality; they won't keep criminals from bringing guns in, of course, but no regulation will, and that's not the intent.
I'm less interested in the general crime argument. We're not having school shooting drills because of gang shootouts in Camden. Prosecution of gun crimes is unlikely to be the intervention that solves that problem.
I generally support all viable gun control proposals; background checks are fine, but won't really address the proliferation and mass casualty problems.
I absolutely do not believe, even a little bit, than amateur gunsmithing is a meaningful factor in gun policy.
I understand that the receiver is, legally, the important part of an assault rifle; I don't so much care about firearm components. As I've said elsewhere, I'm also not generally interested in confiscation of firearms; most people who own them should be able to keep them.
Ironically, with licensure, we could probably eliminate a lot of weird NFA regulation as well.