Friend,
So far no one has asked you the most important question: What do you plan to do with this gun? If you are a historical re-enactor type and want a gun that appears as if it would have when new back in the 18th century then natural steel finish is probably what you would choose. Most original gunmakers did not spend the time to apply a finish to a gun barrel unless you are talking about a "better" gun made for a top-dollar customer. If you want a gun that reflects an original after many years of use then you would probably select one of the barrel aging recipes that have appeared here. If you want a serious hunting hunt then you would finish it matte brown of matte black. There are some references to barrel browning in the 18th century writing that suggests that browning was done by the owner. A mixture of vinegar and rock salt can be wiped on a gun barrel to produce a mottled brown. I remember reading that Roger's Rangers were instructed to "brown the barrels" of their muskets.
The finish you choose depends on what you plan to do with your gun. My smoothbored gun, "Turk", has a browned barrel.
Best Regards,
JMC
