Lots of good technical talk here and that's important to some.

Lets talk about the ackley Improved.

for almost all the cases we will discover (if we have the correct pressure reading equipment) that the ackley Improved cartridges actually offer very little over the parent case in terms of velocity. In some cases the gains are less than 50'/sec and in some cases there is no gain at all.

Possible exceptions are the .250 savage where greater gains to case volume are made than a .30-06 for example. There might be others but far and away the benefits of the AI cartridges are way over stated, exagerated and in general pure BS.

At best you might get 50'/sec gain with a .35 whelen improved over the .35 whelen parent cartridge. Bear in mind that a major league baseball pitcher can throw a baseball at 150'/sec........if that puts it in perspective.

Now to the question of the .338-06 verses the .35 whelen (improved or not) IMO it's six of one and a half dozen of another. There is nothing you can do with one that you can't do with the other. There is no game animal on the planet can tell the difference. Personally I would prefer the .338-06 but out of pure prejudicial reasons and not out of any practical differences. Add to this the 9.3 X 62 mauser and we have a fine trio of near twins.....or triplets as the case may be.

All of these have great range for their bullet weight and immense knockdown power for big game and (if legal) for dangerous game as well.

Just one more fly in the ointment here.....as good as these rounds are there's very little gain in any of them over the good old .30-06 for big game. If you need more than a .30-06 you really ought to be looking at a .375 H&H.