I have noticed recently more people mentioning head position parallax for range finding in HFT. I understand reading the severity of blur of targets not at the scope parallax setting and learning what targets look like to approximate range from how blurry they appear and other tell tales your scope can show. However, its when people mention moving your head position around behind the scope and checking the parallax I am a bit in the dark. Is it a case of moving head position and if the target moves "a lot" relative to the cross hairs its further away than if it "moves a bit". Do you just have to learn this movement or do you measure the movement using the mildots in some way? Like bracketing? I may have the wrong end of the stick, but any help/explanation would be most appreciated.