John,

I don’t see any trouble of having a modern double in 8X75RS. Pressure for the round (Pmax(MAP) 55114psi 3800 bar. Pezio Cip measuring method) is the same as for 30R Blaser, 8,5X63R, 7X65R Brenneke or 6,5X65R RWS. 8X65RS the figures are Pmax(MAP)58740psi 4050bar.

A double in good quality material shouldn’t have any problem with these cartridges. There been more than a few doubles built for hot rocks like 300 win mag, 458win, 375H&H and they seems to hold up well- Personally I don’t like rimless cartridges in a beak top action design.

If I should rechamber some old double of questionable life and unknown material quality, not been re-proofed I would look at rounds with the lowest possible pressure, in fact, I would most likely not bother with a double that not been re-proofed.

Cheers
Johan