.375H&H - standards in SAAMI and CIP in pezio pressure is 62,000PSI - both US and European.

CUP and CIP (copper pressure) listing is 53,000 and 54,000 respectively.

The 8x75RS is listed as 55,000PSI in CIP rating, 7,000 less than the .375H&H.

I suspect rim/head sizes are close, but do not have that data at hand.