Power Pistol is definitely a flake powder.
Hodgdon Lil'Gun has built itself quite a reputation for erosion in big bore revolvers, would that make it a contender here?
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.