Wouldn't a load that shoots like that for 15 shots at 300 have to be in tune? Are you sure your barrel is a true 1:9? I'd want to test that thing in steps (500, 600, etc.) out to 1k if possible to see just when that vertical begins to show.
Usually a load that shoots like that at 300 will tune decent at 1000. But it is not always the case. Where it falls apart is not really important. What is important is, not falling apart at the distance you want to shoot at. MattWouldn't a load that shoots like that for 15 shots at 300 have to be in tune? Are you sure your barrel is a true 1:9? I'd want to test that thing in steps (500, 600, etc.) out to 1k if possible to see just when that vertical begins to show.