as the law stands you can have it set at 12 so long as the grub screw is tightened, your ok its legal only if you have to adapt it by means of a tool to take it up, not manually. basically if you get a tug your ok as long as grub srew is wound in on wheel and you cant physically turn the wheel without the means of a tool to do so. i know this cause a good friend of mine works for the firearms department.