The following data was for the 300 Tomahawk with around 115.5 grains of water capacity.
With the 210 we used H50BMG 100 grains in a 34 inch barrel, 3300 fps but accuracy wasnt as good as the 190 Berger's at 3600 fps.
I dont think the H50BMG was at max load either but it was very close to max capacity for the case Hodgdon says 105 is a compressed load. The barrel was a 1:10 Lilja 34 inches long. The 190's were exceptionally accurate at 3600 fps.
Hodgdon site says 96 grains for max in a 300 ultra with the 190 gr Hornady SPBT at 3200 fps. I'd say the Retumbo would have been a better choice but it wasnt available back then and it was a gun I built for a buddy and I no longer have access to it.
Cartridge Loads - Hodgdon Reloading Data Center - data.hodgdon.com