Can't help you out with Iowa but it might serve you well to attend one of Shawn Carlock's shooting courses.
Report On Defensive Edge Long Range Shooting Class
The main thing that changes for you between 500-1,000yds is wind. Depending on the terrain and weather you can have the wind change as much as 3-4 times between shooter and target at long range and so accurately doping the wind becomes incredibly difficult.
If you have taken the time to work up to a good accuracy load and have a ballistics calculator the doping part is easy once you learn to read the wind.
The other part which just takes a lot of practice is learning to get really steady with a consistent mount and really good discipline on the trigger. The further you shoot the more every error is magnified down range.