Hmm--seems that I might have to learn how to make a historic varnish too! In my TOTW catalog, it says that " in The Rifle Shoppe Catalog, Jesse Melot reports that he has examined 14 rifle which retain their original rifling. All have 1 turn in 49" twist, .018 to .021" round bottom grooves, .078" to .085" width." "Most original 1803 rifles show evidence of a brown varnish, not the ordinary linseed oil, as might be expected during this era."
On the Rifle Shoppe site, it says that they will put the original proof marks on their 1803 barrels, if they are sent back to them. Hopefully, Jesse will still make good on that deal! This is going to be a fun project!
-Cal