I Have Issues! .308 Win Problem

[C.E.Smith043]

Couldn't agree more. It would be great to do load development out to the range you want to shoot, IF, you could eliminate the environmental impacts on accuracy along with the shooters impact as well. However, I have not figured out how to accomplish this.
For me, it seems more practicable to do load development between 200 & 300 yards, depending on the range. My range is fairly well protected from wind by trees. Also, there is generally little to no wind in the early hours of the day. So I can assume that my groupings are more a result of the load and not outside influences.
Once you have the load, practice at greater distance, to me, seems to be more logical.
I may be wrong in this, but that's my logic.

Your thinking and logic is not wrong....its just not always 100% right. Like the op stated "consistently grouping 1/2 MOA or better at 300yards, however, can't shoot a 1 MOA at 600 yards" you will sometimes encounter a problem such as he did. This kind of grouping problem doesnt follow logic. I personally have seen guns group better at a longer distance than a shorter distance. Dont ask me to explain it because I have no answers, but I personally have a 17HMR that will group tighter at 75 yards than at 25 yards. And yes I adjusted the parallax out , This is another situation that blows logic out of the water. And im not joking that i scratched my head so much when i discovered this, I rubbed a bald spot. I was baffled.

 

[dreever]

Do yourself a favor and buy a box of Berger 175 gr OTM Tactical bullets. Best bullet I've found in my .308 GA Precision Hospitaller.
I use CCI 250 magnum primers, Lapua brass, 43.3 gr of Varget seated for max magazine length in my AI mags.
2615 fps from a 24 inch Bartlein 1 in 11 twist.

Danny