I Have one and with the stock sights it shot pretty much dead on with 300gr factory loads. Those heavier loads you're shooting will probably shoot higher at the closer ranges. There 300gr loads will probably be closer to point of aim. I later installed a Williams recever sight on mine, but I have not shot it enough to really get it dialed in yet. I think it is going to be fine with standard 300gr factory loads, but might require a taller front sight, with heavier loads.
