Rule303 - that is interesting. Mine was originally a .358 Norma which I converted to .375H&H in early 1974 with an unfired 602 .375 bl. I bought from Ian Dingwall, a gunsmith in Richmond BC. The barrel came off a BRNO .375 H&H 602 that was purchased simply to convert to .505 Barnes Supreme. I fired that one - spun me around like a weathercock. 125gr. IMR3031 and a 600gr. Barnes, seems to me was the load @ 2,700fps, IIRC. That would make about 9,700fpe from an 8 1/2, maybe 9lb. pound rifle. That was a long time ago.
I'm pretty sure my .375H&H held 5 down, same as when it was .358 Norma.