Here is a link to a post in a thread on SSW's that contains some mind blowing video and will open up a whole new way of thinking about breaking pitches that are not dependent on the Magnus Effect. I have been following this thread for quite a while and due to the scientific terms used it has given me numerous headaches, at times it is a difficult read. What I don't know is how it applies to softballs, which are bigger and heavier than a baseball, but also less dense.
You can throw a screwball without "screwball" spin, notice the seam orientation differences in the side by side video.
You can throw a screwball without "screwball" spin, notice the seam orientation differences in the side by side video.