I would like to extend my effective kill range from 600 yards to 800 yards. I feel confident at 600 at this point but have not shot much past that with my 300 Win Mag. I did shoot once at 1000 yards and got an 8” three shot group. This load typically gives me sub 2” groups at 250 yards. In looking at a ballistic program I see that temperature, elevation and velocity make a significant difference at 800 yards but not so big a difference at 600 yards. I was surprised to see that temperature made a difference. I would have figured that it would not matter what the temperature was. Why/how does it affect trajectory? My load is using the Barnes 180 TSX at approximately 3070 fps. The problem is that sometimes the velocity is 3090 and sometimes it is 3030, depending on temperature and who knows what else (I am using RL22, perhaps I should be using H4831 which supposedly is less sensitive to changes in temperature). I have a Leupold 3.5-10 with the Boone and Crockett reticle and would plan on using the 500 yard aim point and then dialing in the needed extra elevation on the scope to be rezeroed at longer range. The worst case scenario difference in trajectory at 600 yards with velocity at 3030 fps, temperature at 30 degrees and elevation at 3000’ compared to velocity at 3090 fps, temperature at 80 degrees and elevation at 6500’ is only 2” but at 800 yards there is a whopping 16” more drop (again from a 500 yard zero) at the slower velocity, lower elevation and lower temperature. So how do you guys account for all of these variables in the field, especially not knowing exactly what your velocity is going to be on any given shot? What do I need to do to take the next step in long range hunting? Thanks so much, Brian.