I normally load 30gr. of Goex FFFG & a 144Gr. .454 ball but on occasion I'll load 35gr. in my 25 year old Pietta 1860 Army & it's pretty accurate for me, say 2-3 inch group at 25 yards.
My 1858 Pietta's get the same loads & can produce roughly the same groupings at 25 yards with my 8" barreled model doing an average of 2 inch pretty consistently.