Generally the issue is not just based on pressure... usually revolves around the thickness of the enlarged chamber walls vs the threaded area of barrel stub (stress risers), the amount of metal that needs to be removed from the feed ramp (also the lower locking lug reinforcement!) vs the backthrust to the boltface, the rebored barrel thickness at the muzzle and the working pressure of the new cartridge vs the old one.

.270 Win

.358 Norma Mag

Bit hard to get proper pressure data on the .358NM but the CIP PMax for the .270W is 4300 bar (62366 psi) vs the .358 NM of 4400 bar (63816 psi).
In this case they are actually quite close... however one real-life test reported a standard factory .358NM load at 63,900 psi... quite hot for a working pressure!

Recoil of a .358NM in the lighter ZKK600 would also be an issue vs the heavier 602.

BTW here's some shots of the ZKK front sight hood, apologies on the quality, it was taken with a 2MP camera camera phone... I miss my Canon A95