4seventy
The following loads were chronoed in my 9,3x74R Chapuis.
These are averages of the left and right bbls.

Norma 286gr Alaska 2250fps
RWS 286gr. Soft Point 2270fps
Sellier & Belliot 285 Soft Point 2190fps
All the following are Superior Ammo loads
286 Woodleigh Soft 2311fps
286 Nosler Partition 2308fps
286 Barnes Super Solid 2314fps. [Shot these before I know better]
300gr Swift A-Frame 2217fps.

The following are reloads that regulate well in my Chapuis.
270 Speer 59 gr of RL-15 2320fps
286gr Noslar Partition 63gr of IMR 4831 2137fps
286gr Nosler Partition 65gr. of IMR 4831 2218fps

I currently use 65 grains of IMR 4831 with 286 gr Nosler Partitions, Woodleigh Softs and the 285 Hawk .035jkt.
It looks like that 63.5gr of IMR 4831 is going to be the best load for the Woodleigh Solids.
Hope this helps.