cheers for that, it's a lot of food for thought!
hasn't scared me off don't worry! it seems like it's best to use more than one of these methods at any time to get an accurate-enough range estimation.
bracketing from the base-plate to the centre of the kz seems like a better way of doing it. at least that is a fairly consistant size. I find the scb-style reticle alot easier to measure sizes with than the more standard mil-dot i had on the gun previously. But it is still easy to make a mistake with it I agree. definately combining with some other methods is the way to go.
was hoping for a quick and easy fix but ah well i'll stop being lazy :P practise practise practise it is then.