On April 19, 1775, approximately 700 Redcoats marched to Lexington and Concord with orders from King George III to confiscate or destroy the colonist's weapons. On that fateful day, members of the local militia confronted the British soldiers and a battle ensued. Thankfully, the colonists possessed weapons similar to those carried by their adversary and were able to persevere.
Our Founding Fathers understood that the common man would form a militia, should one ever be needed, and so should be armed. Thus, the Second Amendment was written. It is intended to protect our rights as citizens to keep and bear modern arms and their essential accessories.
During the Revolutionary War, a modern firearm was the musket; today, it is a rifle, such as the AR-15. Prohibiting these types of arms and their corresponding accessories would be a direct infringement of our constitutional rights. This is a right all Americans, in all 50 states, are entitled to. A right that is not legislated to us, but is endowed to us by our creator.
If one were to argue that these types of weapons were not thought of when the Second Amendment was drafted and so are not protected by it, I would ask why the First Amendment protects the Internet and television. These media were not available in the 18th century, so perhaps the First Amendment should only apply to print media.