The debate for rifled barrels in paintball is a long heated debate that I won’t try to enter here. What I will do is discuss rifling and how it could potentially affect the accuracy and velocity of your shots.
But first, a quick refresh on rifling. A projectile is inherently unstable even in high speed flight, to overcome this inherent instability you put a spin on it (NASA even used this principle on their interplanetary satellites). In real steel firearms this is accomplished through rifling. However, in real steel the rifling cuts into the outer portion of the round, leaving behind a fingerprint forensic scientist often use to tie projectiles to a particular gun.
In paintball a spin is definitely a desired effect as it will help stabilize the flight of the not-so-aerodynamic paintball. But due to the gelatinous shell of a paintball the rifling can’t cut into it to induce spin without risking a high number of barrel breaks. So the rifling inside a paintball barrel is smoother than you would find in a real steel firearm.
This is where the debate really heats up. If the rifling can’t cut into the shell to induce spin, how does it supposedly work? Because a rifled barrel isn’t 100% smooth you can’t get a good seal around the paintball, leaving gaps in the rifling grooves. Some argue that the air flow through the rifling will induce spin on the ball as a result. Others argue that what you lose to the rifling in terms of velocity isn’t enough to make up for what little spin you may get from it. In the end, it’s up to the player to try it for themselves and make the decision on whether or not they want to use a rifled barrel for round ball.
Notice how I said round ball in that last sentence? That’s because there is a place that rifled barrels excel in paintball: First Strike. Due to the design of first strike rounds, the fins on the back of these paint projectiles can catch the grooves from rifling and get a good spin as a result, increasing and already accurate rounds effectiveness. Even Macy Works Shaped Projectiles would potentially benefit from this due to the compression ring designed into the round getting caught on the rifling of the barrel, thus inducing spin.
For every round ball rifling evangelist there’s an anti round ball evangelist saying the exact opposite. I encourage you to experiment for yourself on which way to go. Look at your play style and make the determination on what is most important to you. After all, I’m just some dude on the internet and I can’t tell you what to buy or how to enjoy the sport, that’s up to you!