I have the AI version of the 338-06 with a 22" barrel, I absolutely love it. I shoot the 200 gr Hornady SP. This is the first year I had it and it performed exceptionally well. It killed a spike bull, a fork horn whitetail, and my mom shot her mulie buck with it also. All 3 were one shot kills, the elk was even a frontal shot and that 200 gr Hornady took it right off its feet. It is now one of my favorite rifles. I have heard the 210 NP is a great bullet in the 338-06 also, but the Hornady shoots so well and much cheaper, that it will be my go to hunting bullet. With the muzzle velocities you have listed in your original post you must be planning on shooting some of the heavier bullets, you will have a hard time keeping up enough energy out to 400 yds besides the trajectory will not be very good. If you like bigger bullets try a 225 boattail at 2600 fps. It will kill everything you plan to. Good luck with your build and let us know how it turns out.