In assessing the actions, PSI is only part of the equation. The rearwards thrust applied to the locking mechanism is a function of the pressure times the internal area of the case head. This implies that a narrow cartridge can be handled by a relatively weak action whereas a wide bodied case needs a much stronger action. Area varies with the square of the radius. This implies if the new cartridge is half the width then then the pressure can be four times the original and still have the same thrust.

A practical example is the Baikal SxS which is available in 30.06 and 45/70. Baikal recommends keeping the 45/70 to sub 28,000 psi loads. However I've heard people claim that because the action can take 30.06 pressure levels, then they can load there 45/70 all the way up. Not so! If you do the maths, 28,000 psi times the internal area of the 45/70 case head produces a thrust equivalent to that of a standard 30.06 cartridge.

(Isn't life a bitch. All you want to do is muck around with guns, ammo and steel and some p*#@k tells you to do the maths!)