Does the Second Amendment protect assault rifles?
Many ignorant and uninformed people reiterate the liberal line that the framers and founding fathers could never have foreseen the weapons available today.
I would say you are right: They probably did not foresee the weaponry we have available today. Does it matter? Not in the least. Many citizens of today have never bothered to take the time to understand what the framers of the Constitution were doing.
Many of the framers opposed a Bill of Rights as they feared these would be seen as an exhaustive list. The true original intent of the framers was that the federal government would have no authority other than that enumerated specifically in the Constitution.
Other framers felt the rights expressed in the first 10 amendments were so important that they needed to reiterate those rights even though no power to regulate or remove those rights was granted to the federal government.
Too many believe the government can do whatever it pleases as long as it is not forbidden by the Constitution; this is the exact opposite of the framers' intent.
The framers intended that the federal government could do nothing unless it was authorized to do so by the Constitution.
By the way, they also felt the need to reiterate this principle explicitly: The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people.
For those who do not recognize it, that is the 10th Amendment.