The improved version of the 30-06 necked up to 33 caliber has been around for many decades. Compared to the 338-06, differences in capacity are not too significant, but it does matter. Further the sharper case shoulder adds markedly to headspace control, which improves extraction and reduces case stretching.

Compared to the 30-06 this caliber shoots 10 percent heavier and 5 percent faster. Best loads with lighter bullets can approach 338 Wincheser Magnum factory ballistics. Capacity is sufficient to provide significant big game performance for most game on any continent. With the lightest bullets, this is a fully functional 400 yard hunting cartridge. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.