It depends on the rigidity of the sine bar and the capabilities of twist. I have a home built sine bar rifler and it's most usefull for a 1-30 twist and slower (muzzleloaders). To do a 1-20 I'd have to have another foot of rack and it would have to be beefed up considerably. For that kind of money (as in not much) you can't go wrong if you've ever wanted to play around with that type of thing. If it is a hand operated as in YOU pull the cutter through, it is painfully slow, but still very enjoyable making your own barrel. You wouldn't want to turn them out in any quantity and think you'd be making any money at it but it is fun to make your own stuff.
Now if your talking about a Pratt and Whitney Sine bar rifler, get over there this instant and pick it up!!!