I have a Pietta NMA Target (more hunting than target sights). Its been an interesting work in progress.
The Rammer is shaped wrong, I profiled the end of it so it drove both balls and conicals without mushing them.
Cones would not hold Remington or CCI Number 11 Caps (seems 10s are rare), I could pinch Caps or get the SlixSprings Cones which I did. If you do go with the longer of the two choices, I had to grind the hammer stop back to get to fire but doing fine. As the gun has no value so I am modifying it as needed (the front sight was raised to bring the POI down).
Cylinders are a lot less than Uberti and I got two extra.
.454 balls do created a band, less than .457 but wide enough (my opinion). .147 roughly vs .250.
No timing issues or any other function type.
The .457 balls were 100 fps slower, I will keep playing with it to find which one is more accurate.