Yes - likely it is, but then max pressure for the case is about 65,000PSI, while the SAAMI 'standard' max. and the standard for factory ballistics for the .35 Whelen is 62,000psi.

The 57mm case Improved will have very similar (1 to 2gr. less, perhaps) capacity as the .35 Whelen, but given the improved case shape for handling pressure, coupled with perhaps raising the bar slightly in pressure allowable, there is no reason why the .35 IMP cannot match 35 Whelen factory ballistics & likely run a bit higher, in the 2,550fps range with 250's - safely.

Certainly loading it to .35 Whelen standards will be more than suffice for NA game.

I find this site fairly useful. The text is also a good read, dealing with pressures and how they are developed.

http://kwk.us/pressures.html