The 460 has the same powder capacity as the 416 rigby and the relatively new 450 rigby. The 460 could be loaded down to those pressure levels. Less pain, more gain.
I have two 500 grain bullet loads for my .460.
1) 87.0 grains AA-4064,500 grain Hornady DGX,Fed 215 mag primer. That load is averaging 2070 fps ie .458 Win mag velocities.
2) 95.0 grains Var-Get,500 grain Hornady DGX,Fed 215 mag primer. This load is averaging 2316 fps i.e. top end .458 Lott velocities.
