A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed.
The first part of the Second Amendment says that having "a well regulated militia" is "necessary to the security of a free" nation. We fought (and defeated) the most powerful country in the world, Great Britain, to win our independence. The colonialists accomplished this by organizing into militias and encouraging everyone with a gun to join the cause. Militias fought the British for four months until our new General (George Washington) organized the Continental Army (using militia forces). Naturally, when the Second Amendment was written, militias were held in high regard. Militias were the equivalent of today's National Guard. Each state had militias that were prepared to join with the Continental Army defend our new country. Our founding fathers realized that if our (White) citizens are armed, other countries would not try to invade our country. So the United States was a super-power in 1789 because we had militias.
Now we have the most powerful military in the world. We have the National Guard. We don't need militias anymore.
The second half of the Second Amendment addresses individual rights: "the right of the people to keep and bear arms, shall not be infringed". This was written in 1789. It gave people the right to have muzzle loading muskets. As weapons evolved, the law did not. Since there were no restrictions on guns, criminals were using machine guns in the 1930s. The National Firearms Act ("NFA") was enacted on June 26, 1934 to deal with weapons being used by organized crime. The NFA restricted machine guns, sawed off shotguns, short barrel rifles, silencers and destructive devices (grenades, bombs, explosive missiles, poison gas weapons, etc.). So before these restrictions were placed on the Second Amendment people could legally possess poison gas weapons. I suppose if there still were no restrictions on "keep and bear arms" we could have our own nuclear weapons.
When the second amendment was written it gave everyone the right to have a muzzle loader. It would be difficult to shoot a large number of children because they can flee while the gun is being reloaded. The Sandy Hook shooter had a .223 Bushmaster (M-4 carbine AR-15 platform) and multiple 30 round clips. This weapon is legal to possess and they're selling like hotcakes right now. This weapon made it possible for the lunatic to shoot as many as six rounds per second and and then slap in another 30 round clip in a few seconds. We need to decide how to make our children safe. Maybe everybody should be armed at all times. Maybe we could all be in police militias. We could all carry .223 Bushmasters with 30 round clips. Would our children be safer?
I believe that the evolution of deadly weapons requires restrictions on people's right "to keep and bear arms". I think it's time to restrict AR-15 type rifles. I think high capacity clips should be restricted. I don't want to discard the Second Amendment. Our founding fathers wanted everyone to have the right to own a muzzle loader. They never envisioned the fire power that we have now.
.223 Bushmaster m-4 carbine http://www.wggb.com/wp-content/uploads/2012/12/weapons-6.jpg
2042 Country Fowler Musket http://www.americanrifleman.org/Webcontent/gallery/59/2042CountryFowlerMusket_PG.jpg