The key is to assemble the barrel and hone it together, this will wear your hone extra, running over the whole barrel, but gets the most important part, the point where the inserts meet the barrel!
For those who would like a visual of vortex shedding, here's a great simulation from a golf ball company of a sphere vs golf ball. Dimples won't work on the flexible surface of a paintball unfortunately!!! https://m.youtube.com/watch?v=GHOoZYhF6r4
That's what makes the circle!