This depends on many things and will vary a lot. Assuming top performance as your stating....
In a 26" 30-06, I would start with the 215 Berger. loading all the way out to the lands making the most available powder space, 2700-2750 should be achievable with certain powders. We were shooting the Hornady 190 BTSP at 2800 fps out of 24" barrels using H4350 and no pressure signs, so 2700+ with better powders and a little longer barrel should be doable.
Then comes what you consider max potential. Do you consider 1000 ft. Lbs, 1500 ft. Lbs, or the recommended minimum velocity the max for elk?
Then comes where you hunt elk. The 8000 ft + I hunt at would prove to have different ballistic max's than a 4,000 ft hunt somewhere else.
For where I live (and hunt pronghorn) at 7000 ft elevation, this is what I come up with.
Max for 1600 fps velocity, 1210 yards.
Max for 1500 ft-lbs energy, 1005 yards.
Max for 1000 ft-lbs, 1410 yards, though the velocity is below the threshold where I would feel comfortable.
Where I hunt elk at would come up with even farther numbers, as it is another 1000-3000 ft higher in elevation. VASTLY different numbers from the 600 yards that most are posting.
Just goes to show, no one situation is the same, and a simple change of a bullet can nearly double your max effective range. The rest is up to you, the shooter.