Joe, regarding your sphere based on a 20 foot radius, I think you would have to take into account the fact that the SS agent was facing towards JFK and picked up the rifle from the floor in front of him. That would make it far more likely to fire to the front than the side and even less to the rear. So the odds can't be based on the full area of a sphere. Maybe a box extending 30 degrees to each side and 50 up and down. More up and down since he was said to have fallen back when the gun fired which overall moves the barrel upward.