I'm almost 100% sure that none of the people who wrote the second amendment ever had the pleasure of seeing a FA weapon. They would then have formed no opinion of them. Since the second amendment was written before these weapons existed, doesn't it seem sort of illogical to apply it to FA guns. Who can be sure that Thomas Jefferson would have wanted them included in the second amendment. If weapons like that existed at the time that the bill of rights was written, who knows what might have been different. Anybody who thinks that they can accurately get inside of some dead guys' heads and figure out what they would have wanted need to get their ego in check. The founding fathers of our nation trusted us to make changes and modifications to our rights depending on what was needed to make society function. The laws discouraging the ownership of FA weapons were passed in the 1930s to help stop violence associated with prohibition because that is what we thought was needed to make the country safe again.
I'm not trying to use my argument to justify outlawing these weapons, I'm only trying to say that sometimes it can be very complicated trying to apply modern situations to 200 year old documents. The best thing that we as present citizens can do is think for ourselves. We were given the power as a community to change laws and make the world better by adapting to new environments. I guess all I'm trying to say is that none of the laws we have are set in stone, and they sometimes need to be reworked to make sense in current times. Sir Newton's laws of physics made perfect sense 200 years ago. Now we know that they are not true (well those of us who payed attention in school know). If we had continued to apply old science to new situations we would not have been able to progress past our own legacy. We have been given the right by our forefathers to think for ourselves. We need to use modern arguments (there are plenty of good ones) to justify the ownership of FA weapons or we'll all look like ignorant kooks.
FA weapons are a tricky beast. I would be hard pressed to be able to justify my need for one. I honestly can't think of any situation in which I would need a full auto weapon, ever. One well placed bullet is better than missing 20 times. But if somebody really really wants one they should be able to have one as long as they know what they are doing with it. I do think it sucks that our government won't make something illegal outright, they just make it so inconvenient and expensive that most people don't exercise the right that they have.