For actory ammo and 600 yards, Hornady makes a match load using 168 gn bullets.
Sold by the CMP, designed for the CMP-GSM Vintage sniper matches.
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It's accurate, but, there is still the debate on 168s past 600. I found they dont work at 1000. One would be better off with the same load using the 175/178 match bullets by Sierra & Hornady respectively.
I use pretty much the same load as hornady, replacing the 168s with the 175 SMK.
So using Berger Bullet's ballistic program, this is what I came up with using my bullets with a 600 yard zero. This is in MOA.
100=24.5
200=12.7
300=10
400=7
500=3.75
600=0
700=-4.17
800=-8.8
900=-14
1000=-20
1100--26.6
Understand that Ballistic programs are only a guide, and must be confirmed at the range. But I've shoot a lot of '06 rounds to 1000 yards, and found those numbers are pretty close in my rifles. What they do in yours may or may not be different. Lot of other considerations apply in long range shooting.
The load I use isnt hot, the MV is about 2700 fps. I shoot it in my Garand, M1903A3, 1917 Eddystone, and my Vietnam Era Model 70 Sniper rifle clone. The latter has gotten to be my "go to" rifle for 1000 yard matches.
Again I've never had much luck with 168s at 1000, either in the '06 or 308.