You touch the gun with your shoulder/cheek - body parts, a high power scope will show you the heart-beats motion horizontally.
I tried shooting 100 meters with any kind of front bipods and tripods also supported the rear with a monopod, got the same visual results. Looking through my 10-50x60 optics.
Building now my own one-piece rest over the winter, will see how that helps "free floating" the rifle and without a human errors.