I use mine and it works every time. I use Federal HIGH ENERGY 140gr TBBC or Winchester 140gr failsafes. Both are excelent and you can get them at Walmart. As for 300 to 400 yard shots it could happen, but if that is all he gets then the guide isn't doing his job to get your buddy on elk. My longest shot has been 130 yards and the closest at 20 yards and most under 75 yards. Make your buddy practice alot. As for heart or lung shot the lung shot will actually kill the animal faster because of the loss of blood pressure. The brain will tell the heart to pump faster to keep the brain supplied with oxygen and therefore bleed out faster and give a better blood trail. A heart shot obviously shuts down the heart and it won't pump the blood out.