Extrapolating data from one cartridge to another of the same bore size depends largely on case volume.

Usable capacity (meaning volume with bullet seated to magazine length) of the .30-40 case is some 2 to 4% greater than that of the .308 Win. case. The same, of course, applies after they are necked up to make the ".35-40" and the .358 Win. The .35 Win. has a usable capacity about 25% more than the .358. Consequently, a reasonably high-density load generating a given pressure in the .358 will yield about 2-4% less in the .35 Krag and one developed in the .35 Win. gives ~25%+ higher pressure in the smaller Krag or .358 case.

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Note how 46 grains Varget in .358 gives same velocity but significantly higher pressure than 50 grains in relatively large .35 Win. case.

QuickLOAD estimates - NOT LOAD RECOMMENDATIONS!