I apologize for my confusion, but if Griffin & Howe indicated the gun was "safe to shoot", did they not indicate with what load?
Shiny barrels in a 136 year old gun with that degree of use almost always indicate previous honing. To give advice regarding a load, it is necessary to know the chamber length, and wall thickness at the end of the chamber and every inch of the first 12" of barrel, and MWT (and where). Were those numbers provided by G&H?
No criticism of G&H, or your gun, but things like this happen with vintage doubles
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