If you're interested in shooting saboted bullets, the 240 grain bullets like the Hornady XTP's usually shoot pretty good with the 1 in 48" twist.
These TC Cheap Sabots make for inexpensive practice ammo. Some of the Dick's Sporting Goods stores sell them.
http://www.cainsoutdoor.com/shop/item.asp?item=302631
And Cain's Outdoor in West Virgina sells just about any flintlock accessories needed.