I think you can look at some of the 1,000 yard reported scores as a guide of what you might be able to do at that range. People winning 1,000 yard competitions are sometimes not able to hold all their shots into a 2 MOA circle. Its not that the equipment cannot do it, it clearly can. Its the wind and the human element. If you 've never shot that distance before, there is a different feeling being back there (a human is difficult to even see with the naked eye from 1,000 yards) and a puff of wind that you missed means you might not hit paper. Whatever the wind effects are at 600 yards, they seem to be doubled at 1,000. The pressure to perform is incredibly high when you trudge that far from your target. That's why I love mostly being able to do it!!!
The wind is also why I got a 6.5x284 for use on the 1,000 yard line. That bullet is traveling the distance .2 seconds faster than the .308, and significantly flatter. Faster and less time in the air means far less wind to worry about. That is why some use the 300 WM and 300 RUM for 1,000 yard work fster, flatter, less wind.
For example, you are using your 175 Federal GMM, and sitting on the line and call the wind as 5-10 mph full value (your 9 O'Clock) - so you dial 7 mph wind into your scope and roll into position. Oops you missed the wind increase, and when you pull the trigger its actually blowing 12mph - end result of that shot is the bullet being pushed 22.3 inches off you sight mark by 5 mph of wind that you didn't realize was there. IF I'm shooting my 6.5x284, the bullet is pushed only 14.5 inches by the same gust.