"I know there is the Constitution that allows me to have my weapons backed up by the Supreme Court..."
This comment is naive on several levels.
First, the Constitution does NOT allow you to have weapons. NO RIGHTS are created by the Constitution. Your rights are inherent to your existence. Rights can be denied by man but not endowed by man. In short, the Constitution simply reiterates some of the more basic rights as a means of reinforcing their sanctity and as a warning to government they are off limits.
As for the Supreme Court, have you not heard of "packing the court?" This single issue is one of the most important factors in your deciding how to cast a presidential ballot. The judges on the SC will control your life for decades. When you can shove aboard the likes of Sotomayor and Kagin, freedom and liberty rapidly become subjective terms. Activists have little concern about the intent of the framers or the literal text of the Constitution. Need an example, probably the most disastrous attack on your freedom by the court in its existence, just look at how the Commerce Clause has been twisted to give the government unlimited power in unlimited circumstances. This single issue could negate everything you believe you know about America.
And, concerning the NRA - yes, they are dedicated to firearms rights. However, that issue is very much secondary to what they accomplish. In a nutshell, the Constitution is only useful as long as the 2nd Amendment is protected. By what means would you resist tyranny if firearms were confiscated. Uh, perhaps you should ask WWII German citizens. Registration precedes confiscation, and that is the ONLY reason government has to control/register/license/permit your ownership of firearms. Without the NRA, this battle would have been lost long ago.