I have been packing my 35 whelen AI 15"into the back country for bear not because its a big bore but it has a nice muzzle brake and shoots extremely well 225gr GK@ 2500fps. Lately been considering a 338 06 AI thinking it may shoot flatter out to 300> is it worth the exspense? I was looking at the 215gr GK's anyone with experience on these two big dogs.

I've shot a .338-06 JDJ Encore for years (very close to the AI). It's a super gun. A Arrestor brake makes recoil a non problem. Always accurate. Mine loves 185 gr. Barnes TSX. Killed a big 6X7 elk with it in UT. I'd say it's definitely flatter than the 35 W.
One thing I noticed with my 3 different .338 Encores (.338 JDJ, .338 Mag. JDJ0 is that they do not shoot 215 Sierra Game Kings to the same point of aim as ALL the other bullets I've Tried (and it's a lot).
Probably taken 100 groundhogs and 25 deer with my .338-06 JDJ. No problems with accuracy. I'm sure it will shoot a little flatter.

Vwhitman thanks for the reply. I have read quite a few comments on other forums about no differances between the two but I cant believe the bc alone wouldn't make a improvment with the lighter 338 bullets, maybe if both shooting 215/225gr or 250gr's. I was not aware of the 160, 180, 185 and 200gr projectiles and I think that helps tip the scales in favor of buiding a 338 06ai.

wvhitman, what barrel length was the jdj and what velocities with 180 and 200gr bullets I am thinking of a 15"bbl+ muzzle brake.

Dasbear
While I can not comment on the 338's, I have the 35-06 JDJ.
Here is a picture of my SSK 15 inch barrel with added fish-gill brake. Total length is 16 7/8 inches long.
Velocity 180's 2700fs / 225's 2590fs

Oh I thought it was 338's you had.I thats a nice looking encore that fishgill looks pretty cool too. I set mine up with a custom stock for a friend that wasn't familiar with high power hunting handguns.