Excellent!
My Maximum developed load for the sized down .375 300gr. Hornady RN was 45gr. H4895. That gave me 2,175fps and sub 1" groups at 100 meters. This load showed mild pressures - totally round primers and no web or above web expansion from sized brass that drops into the chamber - I mean "0" expansion on a one ten-thousandth's michrometer (not calipers).

In this 57mm case, Varget is a bit slower than H4895 so it produces slightly slower speeds, but reasonably close - at probably 2,145 or 2,125fps.

Incidentely, the .350 Rigby, which has bullet diameters at the bore size of the 9.3 at .358", put a 300gr. Kynoch factory load listed at 2,150fps, IIRC from John Taylor's book, which showed a photo of a lion taking one in the face in a charge, point blank. Impressive. Man - just thinking, been a long time since I read that book from the local library.

2,200fps is not too shabby from 286gr., or 2.300fps with the 270gr. Speer (bit soft for me), either. It will easily do 2,250fps, maybe even 2,300fps with the 286gr., I'm sure.

The same chambering in a M98 action will easily duplicate today's underloaded 286gr. factory 9.3x62 ammo - 2,340fps with 286gr. and not stress the action, either.

Note, with 286 Hornady's at 2,200fps and Norma 232's, Vulcan or Oryx at 2,450fps, this is a GREAT NA game ctg. or even most shots at African plains game, I'm sure.

Sized down 225gr. Hornady Spire Points at 2,550fps, with their 1/16" thick jackets, would do for most all NA game.

They also shot under an inch at 100 meters.