You just have to find your own range that its on at and make note. zero it in at 100 meters, then fire it at 200 meters and make note which ring is correct, maybe ur firearm will be dead on 1st ring at 225meters, and so on and so forth.
I have the 4.5x14 on my .257 weatherby mag, and i find as follows...
200 meters zero
410 meters 1st ring
665 meters 2nd ring
800 metrs 3rd ring
1055 meters 4th ring
On my 30-378 weth. mag i use the new Leupold 6.5x20x50 , wish it had the BDC. The scope is a good one for any standard cartidge like 308-06-270-7mm etc.