Martin S ~~ I sold that Golden Age Arms Company flintlock longrifle a long time ago and have no pictures of it other than the ones in my memories.
Hungry Horse ~~ All of my flintlock longrifles had 1:48" twist rifling in them.
*(#1)* The Douglas GAA .45 caliber, 13/16" straight octagon barrel,
*(#2)* A late 1970's, Getz, swamped octagon, .50 caliber barrel that was equipped with a factory coned muzzle,
*(#3)* An early 1980's, Getz, swamped octagon, .62 caliber barrel, also equipped with a factory coned muzzle.
I don't know if it was just providential good luck, serendipity, or what, but all three of those longrifles, each coincidentally equipped with large Siler flintlocks, and each equipped with a simple drilled touch hole; were capable of consistent, sub-M.O.A., 5-shot groups at 100 yards as long as the shooter did his part.
I've been blessed by God with lousy, multiple negative diopter eyesight ever since I was a pre-teen kid. So, when I shot each of those rifles, the 100-yard 5-shot groups usually averaged someplace between 1.5" to 1.75". But, when men with much better eyesight than I possessed shot them, the 5-shot groups usually shrank dramatically to below 1".
I had no mentors in learning to shoot that first longrifle and each subsequent longrifle. All of the information that I started out with as far as that .45 caliber GAA longrifle was concerned came out of articles published in Muzzle Blasts magazine, the Gun Digest Annual, the Dixie Gun Works catalog, or the original Lyman Black Powder Handbook. Everything else was self-taught and the result of trial and error.
As a result, I picked a 0.445" diameter × 0.005" under nominal bore diameter ball mold for that first rifle. Not knowing any better, I followed up with the same choices for both the .50 caliber and .62 caliber barrels; a 0.495" diameter ball for the .50 caliber barrel, and a 0.615" diameter ball for the. 62 caliber barrel. The final powder charges were 55 grains of fffg black powder for the .50 caliber barrel and 70 grains of fffg black powder for the .62 caliber barrel.