Huvius, apparently the bore of my rifle is similar to your rifle. Also, I will start out with 2f black powder.
Huvius, are you using a hard, grooved bullet of soft pp bullet?
Daryl, using lube wads seem to work very well with the limited bpe shooting I have done. With the exception of some oval bore Lancasters, all have accurately shot with a veg wad over the powder, a soft wax wad, and a second veg wad between the wax & bullet.
Brian, the Lincoln City gunsmith that sold me the rifle, said that a 458" bullet would slide down the barrel to the choke. He also said the barrel has a gain twist and is choked about 4" from the muzzle.