It was asked in another post what effect do riffled barrels have on spinning a paintball, not drilled holes, actual rifling like in real guns. This is a good question and one that was explored by our research team.
In theory spinning a projectile on the axis of flight adds gyroscopic stability as well as averages out any imperfections in the surface air flow. Paintballs leave a bad turbulence wake behind them that "walks around" the back of the ball as it flies through the air. This is the main cause of a paintballs inaccuracy as the turbulence tail drags the ball around sideways in flight. Spinning the ball should create a tornado like vortex in the back of the ball thereby evening out all the turbulence so the ball is not pulled any particular way.
So great you say lets do it and get more accuracy!! Well if it was possible it would already have been done. The problem is the liquid fill, when you rotate the shell, the liquid tends to stay where it is. The best example of this is a glass of water with ice floating in it, when you rotate the glass the ice stays in the same place (you have all seen it). So if you can grab the ball hard enough to go from 0 to about 10,000 RPM's in 5 thousands of a second (remember TechTip #1?) Yes the shell is spinning but the fill is not. When the ball leaves the barrel the viscosity of the fill slows the shell down but the fill's rotation is speeding up from the shell too, so you get an almost instant reduction of the RPM's out of the barrel. The balls rotation does not come to a complete stop because the shell does impart some spin to the fill. In order to test this properly we actually developed a gun that spun the barrel, with the ball in it, up to 30,000 RPM's and then shot the ball out.
In this way we knew the ball and the fill were completely up to speed when it left the barrel. We had visions of a spinning barrel paintgun that would make that high speed turbo wine! Unfortunately this didn't improve the accuracy because the ball is still too light.
As a final test we developed a barrel that had three razor edged knife blades running down the length of the bore. Using our plastic paintballs they wedged in the blades perfectly and we spun up the barrel and fired more test rounds. Because the knives would cut the ball we could examine them after the fact to see if they were rotating in the barrel etc. Again unfortunately we saw no improvement in accuracy and gave up.
Based on this data we believe round paintballs are too light and have lousy aerodynamics to expect any more accuracy than what we are currently getting. When the military came to us and wanted a more accurate non lethal system we made a bullet shaped, spin stabilized paintball that far outperformed any equal weight round projectile. Accuracy by volume has been, and will remain, the best way to score eliminations.
