I don't know, a 30 Gibbs might be kind of fun.
But there are a lot easier ways to make brass than the old oil shower method.
Personally, I would run an 8mm tapered expander button through a new 06 case and then neck it down for a crush fit in the Gibbs chamber.
It would then fireform as easily as any other improved case.
Wolfe's "Wildcat cartridges Vol II page 803: Roger Stowers gives reloading data for many bullets with various powders. I would consider his load data as highly optimistic until I worked it up with pressure trace equipment.
For instance he quotes:
3261 fps with a 150 and 59 gr IMR4320
3129 fps with a 165 and 63 H450
3070 fps with a 180 and 66 gr of IMR4831
2871 fps with a 200 and 64 gr of H4831 or 61 gr IMR4350
2688 fps with a 220 and 63 gr of H4831
