Hello Godzilla,
Back in the day I started with a Thompson Center Hawken, it shot fair.
Then I decided I wanted to build a kit, I decided on a CVA Frontier Rifle.
The only problem was at the time I could buy a completed rifle cheaper than the kit.
So I purchased the rifle, stripped the blueing off the barrel and attempted to brown it.
That rifle would shoot 10 times better with round ball than the Thompson Center.
A slow twist is needed for round balls, 1/66 is what the old CVA's were, the old Thompson's were 1/48.
I'm sure you will be satisfied with your re-bore, as long as the rifling is correct.
Unfortunately we don't do much round ball shooting anymore, it gets harder with age to see the targets.
AntiqueSledMan.