Gary-


I hear you on the nitro/cordite paradox detail.
This could really be anything, and I suspect it's for a muzzle loading rifle.
That would be a good bit of grease for a ~.56 caliber black powder rifle.

I will look forward to seeing if you come across a 20bore (.625) or a 16bore mould.
One of my 16bore cartridge rifles has groove dimensions closer to 14bore (built for the thin brass case...)





Cheers
Tinker