Cayugad,

Nice find there. I have the same rifle in flint. They have .010 deep rifleing and are 1/66 twist. Some of the later models were 1:38 or 1:48 twist. If it's 1:66 twist you have yourself a tack driver.

Try out my favorite load if you wish. Might save some tinkering time. I use 85 grains of Goex 3f; .495 Hornady ball; .018 Criso lubed patch and a .54 Wonder wad. Try it out; these guns love Criso as a patch lube! The Wonder wad helps a bunch too.