i'm looking at getting an older 9.3x62 rifle - think it was made between 1910-1920.

Shank has the the reference above which i believe means it was proofed for 37 grs of cordite with a 250 gr bullet max.

When I look at equivalent loads with RL15, seems like a light load for a 9.3x62 and the 250 max bullet surprises me.

The cordite 37-250 max seems like proof mark for a 318 not a 9.3x62.

Don't want to get the gun if it would not be an option to shoot modern ammo and take it to africa - curious if anyone has an opinion on what I could expect?

It also says BAR 5850 on the other side of the shank, and 818 EX above the proof mark.

Any insights would be appreciated. Thanks

Sounds like a rebored 318.
Has there been a chamber cast, bore slug, or anything
which would lead you to think that it is in fact a 9.3?

Are we talking about an English double?

English bolt rifle. 9.3x62 on the barrel.

Also 818 EX above the proof mark.

A rebore makes sense!

The "8" is probably a heavily struck "3" for 318.
I have one which was rebored to 35 Whelen.
This was very commonly done once factory ammunition and .330" bullets got scarce.
The 318 and the 35W can both be made from 30'06 brass and the 9.3 is close enough dimensionally as well that it is a natural choice when reboring a 318.

For the record, 9.3x62 shouldn't be made out of 06 brass, but it will clean up an 06 chamber.

Plus one on Ryan...The practice of making 9.3x62 from 30-06 brass is not recommended, even though some insist on doing it...An experienced eye will see a bulge in the butt section of that 06 reformed brass, and case life is minimal if you full length resize, and you should with any DG rifle..Besides 9.3x62 brass from PPU is cheaper than 30-06 brass from all makers other than PPU..and PPU is good brass. I use PPU in most of the calibers I own and it last forever..Graffs & Sons 9.3x62 Brass is PPU.