If you're trying to hit rabbits for example at 600yds, the .223 is not the answer even with heavies in a fast twist. Wind is the enemy. The 6x47L shooting say 90+ grainers would be in the ballpark. 800 is about 3X as hard as 600 on varmints, certainly in any wind.
I'd say a .204 up to 350yds, max 400, then drag out the 6x47L for more challenging stuff. Where we shoot, 350yds would cover 95% of bunnies I'd guess.
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