I'm not a big fan of target shooting but did occasionally partake by borrowing the occasional L39 or sometimes the accurate L81's that were housed in the Armoury. The old RQMS that used to book the zeroing range and come down with me for a shoot told me that the real shooters zeroed the rifle at the 0-0 fixed/sliding scale mark on the range scale and ignored the rest. They just went by the clicks on the scale. Knowing that. say, 10 clicks was 200 yards and 12 clicks was 200 metres and so on up to 900 yards or metres. That meant they could use any of the sights (depending on the clicks per revolution of course. So any sight that was on the rifle was acceptable.
I also found it beneficial because by doing it this way, it was deemed to be an official sport so ammunition and mileage was on the house so to speak!