@InfraBlue,
That is incorrect. Machine guns were not extensively used in murderous crimes to begin with.
Neither are AR-15 rifles used extensively used in murderous crimes today.
Additionally, merely being used extensively in murderous crimes is not in itself enough to provide a compelling government interest in restricting access to something.
That is why it is unconstitutional to restrict access to handguns despite the fact that they were used far more extensively in murderous crimes than machine guns were.
That's why it is unconstitutional to restrict access to handguns despite the fact that they are used far more extensively in murderous crimes than AR-15 rifles are.