How far does a non rifled cannon fire vs a rifled?

Even though it's possible that a rifled gun will shoot further than a smooth bored gun; that would certainly be the exception rather than the rule.

Generally speaking, the rifling is for accuracy...not range.

And, generally speaking, a smooth bore would shoot further than a rifled gun; because it has less friction than a rifled gun does. That's why the M1 Abram MBT has a 120mm smoothbore; to obtain more velocity. To compensate for it's loss of accuracy, due to a lack of rifling; the M1 tank fires projectiles which un-folds fins upon exiting the muzzle.