NRA is currently the most powerful lobby group in DC.
The argument behind the 2nd amendment intends to be that people, when faced with oppression and tyranny, should be able to defend themselves and overthrow such government, therefore they should be constitutionally supported to bear arms that include automatic and semi-automatic rifles, which were the standard firing devices back in the civil war. Interestingly, nowadays the US military employs more than conventional weapons. So should the 2nd amendment increase its scope of content and allow people to own nuclear bombs and missiles for personal purposes?
I'm no expert in legal matters, and I know that I inevitably fall into the "too young too naive" category. But it's obvious to me that the constitution needs to be interpreted in the context of its time and background, law is meant to create order and preserve justice, not bring chaos into people's lives.