The 375 Ruger holds 101 gr H20 volume and the H&H 93gr H20.

The factory round is a high pressure round @63,000 psi. The primary advantage is the standardized length so what advantage whatever does a 300 Ruger or 338 Ruger give?? Why even bother??

The bullet velocities may go higher with the Ruger but why bother? Develop a reliable load at lower pressures shooting the same bullets as the 375 H&H in a shorter action more handy gun and go hunting!!

If I were going to wildcat the cartridge I would look at a 358 cal Ruger cartridge in a lightweight carry bolt package. A 416 wildcat?? Although the ballistics and pressure data suggest the possibility IMHO I believe 416 Rigby is a better natural fit for an African environment with lower cartridge pressures,triple digit temperatures and DG waiting to deal you misery if a rifle screw up occurs.