I am in the camp of opinions here that believe you need to get closer. Hone those stalking skills. I have killed a few elk, the farthest was 340 yards as measured on the laser. The rest were all under 150. My fondest memory is of the bull that I stalked up a draw and shot at about 65 yards.
I have played with shooting out to 700 yards, lots of little things out of your control and they REALLY start to show up past 400 yards. I would feel comfortable shooting 450 if conditions are right, beyond that the animal would very likely get a pass from me.
I am rather fond of Nosler Partitions but there are other good choices.
