Since this is a benchrest forum . . .
It is hard to get good .30/06 brass. I use to shoot a 6.5/06 AI, and with Lapua brass, had to throw away about half the cases for excessive case wall variance. Two different lots.
Of course, you could start .270 or .280 brass, just more work.
After that, it is all bullets and barrels. A very good barrel chambered in the '06 will outshoot a mediocre barrel chambered in .300 Win Mag. But generally, anyone going with a .30 for 1,000 yards will use, as a minimum, a .308 Norma magnum. I know one guy who shot a .30/06 AI -- he worked for Lenoard Baity -- and he did well.
Brakes are allowed in all 1,000 yard benchrest matches for the 17-pound Light Gun. In IBS Heavy Gun, (no weight restrictions), brakes are not allowed. They are int the other two sanctioning bodies (NBRSA and Pennsylvania).
Danny Brooks was at least twice the IBS National Champion -- he used a .30 Win Mag, I think in both Light and Heavy, heavy for sure.
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If you stay with bullets under 190 grains, the '06 should do fine, particularly in the Ackley configuration.
The belt can cause a problem in any chambering that uses it. The case grows just a touch in front of the belt, and after a while, not even Larry Willis' collet die will size it. Current thinking with some of the Pennsylvania 1,000 yard shooters is to get a reamer very tight on the belt, and headspace off that, rather than the case shoulder. Any case with a bit too long belt has to have the belt turned to fit in a lathe. None of this is SAAMI, of course.
Probably more than you wanted to know.
