There is a rangefinder when zoomed button...ez mode is to map that to your fire button which will auto range every time you shoot (which is very OP), otherwise select another option and click on that once aimed on target. at 125 m not too much to range find as the default is 100 m. I would encourage you to do a custom game search and join a breakthrough game on liberation peak. Attackers and defenders get some great sniping points 100-200m apart. That map/mode is my go to for anything Sniper or DMR related. If you need longer distances throw in Firestorm, which will let you shoot up to ~400+ m.