The Bill of Rights are simply the FIRST ten amendments to the Constitution.
They were added to the Constitution AFTER it was ratified by the States.
The people OF THOSE TIMES supported those amendments, just as Americans since then have supported amendments to support abolition of slavery and the right of women to vote, to name but a few.
We are no more bound by the amendments of the first American generation than future generations should be bound by amendments we support today. That's the whole point of a democracy, after all. It evolves, grows, learns, etc. - tempered by experience and reality. Not frozen in time.
Those who believe any amendment is beyond modification or even retraction simply do not understand how our liberal democratic system was setup to function.
This is what Thomas Jefferson had to say about change:
"I am not an advocate for frequent changes in laws and constitutions, but laws and institutions must go hand in hand with the progress of the human mind. As that becomes more developed, more enlightened, as new discoveries are made, new truths discovered and manners and opinions change, with the change of circumstances, institutions must advance also to keep pace with the times. We might as well require a man to wear still the coat which fitted him when a boy as civilized society to remain ever under the regimen of their barbarous ancestors."
As a gun-owner myself, I'm quite content to use basic defense weapons for target practice. I don't need or want anything more. And, even if I did, I would give up access to higher-grade weapons as I'm not so selfish as to demand a right to recreational high-power target shooting at the expense of crazy people using same high-power weapons to decimate my fellow citizens.