A better interpretation imo would be to look at the moral principles laid down in the 2nd amendment. Security, maintaining order, and self-defense are all things that have roots within the 2nd amendment. Security is in the actual text, maintaining order obviously flows from the well regulated malitia and security, and self-defense is often attributed to owning a weapon.
Now why can we not fire a gun in a densly populated area, because this does not flow from the 2nd amendments moral principles. You are not protecting yourself or others, maintaining an orderly and secure society, in fact you are doing the opposite.