I have a 338-06 AI under construction, so it will be awhile before I have real world data. I did order Norma 338-06 headstamped brass. It holds 71 grains of water to the case mouth. If the AI version gains 7% capacity, final case capacity should be around 76 grains.
Research I have done regarding 338-06 chamber dimensions indicates that there will be enough freebore to seat long bullets, such as the Berger 250 and 300 EH, even with the case neck (or nearly so). Though I probably will not use bullets of this weight for hunting, I expect them to be good long range practice bullets at reasonable cost.
I am taking a hard look at the Cutting Edge 338-200 MTH. It is made to be seated to 3.340", so it will feed from the mag. Based on QL calculations, I should be able to push it to 3000+ fps from a 26" barrel, using RL-17. With a .570 bc, that should make for a heckuva combination from a sporter weight rifle.
I am interested in trying the Rocky Mountain 225 ULD's, though they will be too long to mag feed.
When I am able to start actually burning powder, I will share my results.