This 10.75 X 68mm case - it is the 8x68 case, isn't it?

If that's the proper case, it will literally have the same capacity as a .375H&H case, if the 68mm case was necked to .375 - thus, in 10.75 it should have lots of capacity for getting up to 2,400fps with 400gr. as it is much over the .416 Taylor, which has been doing that for 40 years.

This is due to the .524" base and .478" (approx.) shoulder.