The why does it say:
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.
You can pretend all you want. But the 2nd Amendment and the related federalist papers make it clear they wanted the ability of the "people" to be able to stand up to the federal standing army. Which also goes to say the arms should not be limited to slow, small caliber hunting.
Here's what I think is the correct answer,
@thackney. I understand, respectfully, that you will disagree.
The natural right is the right to self-defense, including that of home and property. Justuce Scalia, I think, understood that, and that is why his landmark Heller decision held, for the first time in the history of our Republic, that Americans have an individual right to keep and bear arms.
Now I understand that the Heller decision was, of course, made in the context of the Second Amendment. If you read the opinion, you'll be astonished at the trouble Scalia had to go to, to reach that interpretation. The Second Amendment is worded in a very peculiar way. It is not worded like that other Amendments describing the rights of Americans. It has a predicate clause about a well-regulated militia, and it - uniquely for the Constitution, I believe - uses the word "infringed".
I don't think the Second Amendment addresses the natural right at all. It talks of ensuring the resources (the men and arms) necessary for the defense of the Republic (the "free state"). I'll go out on a limb here - I think the Constitutional is as textually silent about the natural right of individual self defense as it is about the natural right of individual privacy, which is what undergirds the hated right of abortion.
I hail Scalia for discerning the missing piece of the Constitution - that we have the natural right to defend ourselves as individuals, and the government cannot us deny us that right. I don't think the Second Amendment ever got us there. I think the Second Amendment, on its face, is concerned with the collective defense, not individual self defense. And because of that, I do not for a minute believe it bars the registration, licensure and insurance of firearms. To the contrary, I believe it anticipates it.