I really like the Ackley Improved family of cartridges - although they are often misunderstood and generally will not fetch as high a price in a used gun as the parent caliber. The general "rule of thumb" with the A.I.'s is 175 to 200 fps over the parent caliber. Sometimes as little as 150 fps - sometimes as much as 225 - generally, you have to go to a slightly slower powder to get the higher end velocity. A lot of "gunsmiths" do not understand how to headspace these guns - but, done right, they will deliver enough of an increase in performance to make it worth the effort; and dramatically improve brass life.

Having said that, I wouldn't personally mess with the .35 Whelan. Bullet selection is so much better with the .338/06 and it fills essentially the same niche.