[lcoreyl]

Ok, I’m going to table the debate of whether drag and magnus are significant in order to clarify the second point I was trying to make: who cares?

remember the science lesson when you learned about accuracy vs. precision (repeatability)?

all the calculations discussed are concerned with accuracy; however, your FIRST concern should be building a shooter with very good precision!! drag and magnus won't cause bad precision.
drag and magnus depend on speed and spin. If you build a shooter that always has exactly the same speed, angle, and spin, then there will be an "accuracy" error, but the ball will land in the same place each time. a few tweaks and you're golden.