My mistake - I was thinking rimmed...
Just what bears the brunt of using a higher pressure round anyway? Is it the hinge, or the action face or what part exactly? I kinda figured "meat" around the chamber was the most important factor.
I used to have a Genossenschaft double in 7X65r and am sure that was a pretty high pressure round.
Didn't have overly heavy breeches either.
Could a normally high pressure cartridge be loaded down since these would be new barrels anyway?
I guess the danger in that is a future owner may assume full power loads are OK to use...