I don't think FFFFg is good for any main charge in these size guns. The little tiny micro, Nano and pico guns using very small charges is the exception. FFFFg is priming powder, very energetic and has excessive pressure use in small amounts.
The Carriage would look good in black with brass gun. Good contrast. Everything all brass--yuck no contrast. I like what you have done with carriage and gun, looks great.
To late to save the mortar its inthe tumbler, a shame. The patina was lovely and the shooting platform has so much charactor.
Both guns are very neat.