If you want fur friendly then a .36 or .40 cal round ball would be a good choice. A .32 (.31) cal round ball is 45 grains, a .36 (.35) is 65 grains and a .40 (.39) cal is 89 grains. You can easily drive these balls to 1700+ fps with 35 - 45 grains of FFF power. The smaller cal round ball barrels will have a faster twist around 1:48. You need a slower twist for larger balls.
If you have a TC Renegade with 1" barrel you can get a drop in small caliber round ball barrel -->
http://www.gmriflebarrel.com/catalog.aspx?catid=1InchInterchangeableBarrels
If you have a TC Hawken rifle with 15/16" barrel in .32 and up calibers -->
http://www.gmriflebarrel.com/catalog.aspx?catid=1516-InterchangeableBarrels
