the k14 which came later in the war was a computing gunsite with a pipper. if you were following 190 you would set it for the 190 ( wingspan ). then turn another dial making the circle smaller until the e/a wingtips were just touching the circle....this calculated the distance. once the gyro driven pipper was on target...pull the trigger. with this set up you didnt have to lead.....but you have to be in a turning or running battle dial it all in. it did prove pretty effective.