Don't be discouraged about poor accuracy from a new gun.
Every cap and ball I've owned wasn't immediately accurate, straight from the box. The worst I experienced was a new Uberti-made Remington .44 Army. At 25 yards, from a benchrest, I was shooting at a target in the center of a 4X4 sheet of plywood.
The first shot hit the edge of the plywood on the ground. The next five shots were all over the plywood. And yes, I had scrubbed that new bore with bronze brush and cleaned it with patches dampened with lighter fluid to remove any factory preservative.
But those first six shots from it had me grumbling. The next six were closer to the target. The third cylinderful hit paper. After that, it seemed to settle down and start to group a bit.
It took me about 50 or 60 shots before that revolver began producing good groups. I was using FFFG black powder, a felt wad containing Gatofeo No. 1 Lubricant and a .454 inch ball.
Today, that same revolver will put six balls into a 2" circle consistently at 25 yards, from a benchrest. It's one of my most accurate handguns, and that includes modern ones.
Yet, the first experience almost had me sending it back.
I can't explain it. I've never had a revolver do such a drastic thing before. But other cap and ball revolvers I own have also shown marked accuracy improvement as they were used. I would guess that tiny burrs in the bore were smoothed over, or perhaps the residue of a petroleum product slowly worked out of the steel.
I can't explain it. I've experienced it, though. Keep shooting that revolver and you'll likely see its accuracy improve.