Do your research. "The average bum" can buy one legally in most states as long as he pays the NFA tax for a destructive device.
You must be amazed that they're not being used to shoot up schools on a daily basis.
Yep, the most serious criminals can and will get anything they want. They are not dumb people.
I think this has gone way off topic. We're talking about limitations if any on the 2nd Amendment. You have to go back to the original intent: being able to overthrow if necessary a government that is violating your rights. If you think about what that would really take in terms of arms, equipment, etc that covers a lot. I think that easily covers high-end machine guns. Do I think it covers nukes, no. This is because there really wouldn't be a purpose for such a weapon if a conflict broke out inside the borders of the country. There would be no defined borders where the "enemy" is located, making a weapon like this practical. Large scale devices like nukes and large bombs are really intended for attacking other nations where you wouldn't be concerned with hitting your own side. Do I think it should cover small explosives, grenades, etc, yes. I don't believe that it will ever be interpreted this way but perhaps it should be. We should possess the means at all times to be able to overthrow the government because they work for US, not the other way around.