At 3 minutes in this video
https://youtu.be/tSZtt26PQug
So he is saying that the common test of being able to blow the paintball through the barrel is not good, right? Its better to underbore which would mean that you cant blow it through but you can push it through with your finger? So you want to go just tight enough so that the majority of the balls you cant blow through, but not any tighter then that right?
Yep, the blow through test is actually the worst way to set up for consistency. I always underbore unless the paint is absolutely inconsistent as hell, in which case I overbore and am sad.
EDIT: Lol at the original post date. Not sure how that one got missed.