I don't have that knowldge, but thought they were either .62 cal. or 20 bore which is actually .615". I thought the Rifle Shoppe's barrels were around .65. Taylor used a .65 cal. ball and it gave very good accuracy.
I would think an undersized ball might lead the bore worse than a groove diameter ball is why I asked. The gas leakage around the ball would tend to sluff off material and plate the bore with it.
Lead might be difficult to remove from the bore's fairly deep rifling. I suggest strips of copper from a Curly Kate kitchen scrubber wrapped around an undersized bronze brush for removing leading, whereever it might be found, in whatever gun. It's quite effective, and more-so than steel wool.