As a side note, the .50 cal rifle I use with ITX roundball was made using a Rice barrel that has 1:80 twist and shallow rifling (.008?). (Actually if my memory serves me, I did this under the advice of Daryl off this board!) It seems to shoot pretty good, but I am not a competition shooter, just a plinker/hunter, so I would imagine that I could probably achieve my mediocre shooting results using just about anything.
Ken