Sounds like quite a find! Congrats!
I have a 461 Gibbs Farquharson too, but seem to have misplaced it somewhere...
I am in the process of working up a load for mine too.
Buffalo Arms has brass (Bertram) but I am thinking it can be made out of other brass too like the 500/450 No.1 and maybe the No.2 Musket.
Is there anything engraved on the rear sight?
Gibbs Farqs often have the bullet weight and powder charge engraved on the face of the standing sight.
Look forward to seeing it!
As an aside, the picture of Selous with the H&H (the one leaning against the wagon)is often mistaken as a Gibbs. In fact, I have gone onto Wikipedia and changed the caption for that picture a number of times, but some "expert" always goes back and calls it a Gibbs again!!
