It may be possible to pack enough #7 under a bullet to get screaming hot velocities, but I was able to get around 1075 fps out of 7.2 grains, and it was a mild, easy shooting round. That is below most max loads, so room to grow a bit, but if the nukes expand at that speed, not sure I'd want to.
The Western reloading manual has load data for #5 and the old style RMR 124 grain nukes. The new style is shorter, so needs a consensus on what COL ought to be for same powder charge. I'd think as long as bullet base was seated to same depth, the old load data would work.