Probably a 1 in 48 twist.
I've tried balls in mine and can't get the accuracy I wanted with them, but I found that using the Buffalo Ball-ets, with a reduced powder load, works very well, and they are not nearly as expensive as the saboted rounds, for practice.
I cut my powder from 110 grains, down to 85 grains, before they quit tumbling
and started to group well, but you will have to play with yours to know what load to shoot.
I tried hunting with them one year, and did not like them as well as a saboted bullet for hunting, but they are fine for some fun hunting cans.