The 2nd Amendment was actually intended to be an absolute right, as it represents the right to self defense, be it from animals, men or governments. That right exists outside of the laws of any government (or rulings of any court). The Bill of Rights was placed in the Constitution to protect the individual from the Federal government. Indeed, the Constitution would never have been passed without the Bill of Rights inclusion.
The only restrictions on the enumerated (numbered) rights are where they interfere with those self same rights of others. So my mere possession of an item, so long as it does not cause harm by it's mere existence, is protected by the Constitution. To whit, if I possess a book outlining an insane homicidal philosophy, that cannot be a crime under the Constitution, no matter how many of my fellow citizens believe so, or how many of their US Congressmen they elect, or how many laws they pass. Now if I act upon the insane homicidal philosophy in that book, THAT is then a crime.
The same argument applies to arms or the ammunition for arms or their components (all of which the British attempted to confiscate prior to, and during, the American Revolution).