I had an EXPS3 on a Sig M400. It was heavy enough it made the rifle feel out of balance. If the rifle was not kept perfectly straight up and down, it fell to the side it was tilted toward. While I liked the dot-circle aim points, they do not automatically adjust for ambient light. Stepping from direct sunlight into shade and they would flare out, adjust and step back into the sun they were invisible. Adjusting the brightness level is slow and a bit tedious if wearing gloves. I passed it on to a new owner at a generous discount.
I am curious what the caliber has to do with using the circle to estimate range? If you mount the sight on a .308 does a man sizes target get larger or smaller?