Good advice, 93mouse - The way I filed the sights on my 14 bore were just like that. The top of the bead is level with the 'ears' of the rear sight. The bead is about 3/32" in diameter. If the bead is held up with it's centre level with the ears, the zero raises 50 meters over the standing sight's lower zero.
; ie: with the light trail-walk load of 3 drams 3F, the point blank sight is zero'd at 50 meters, level with the ears gives a 100 yard zero, same as lifting the first leaf.
; With the heavy hunting load, the rear leaf is zeroed at 100meters, while levelw itht he ear's tops is a 150 meters zero - same as the first leaf.