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Paintball Barrels, everything you need to know.

Probably the most overlooked part of your paintball equipment but arguably the most important, and certainly the best upgrade you can ever make to your paintball gun. There are as many myths about paintball barrels as there are opinions. Most people really don't have a clue. This article is aimed at putting to bed some of the myths and give you the real info on paintball barrels.

Spinning Paintballs

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, 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.

So, the myth that barrels that spin the ball are more accurate is completely untrue.

Barrel to Bore match, does it make much difference

Does having a good paint barrel match improve your accuracy? YES is the simple answer. How does it do it? Well, that's very Very simple, if your paintball gun shoots with a consistent velocity the paintballs will tend to follow the same arc, thus improving accuracy. It technically is making your gun more consistent which is a better term than accuracy.

Historically there were many theories about paintball barrel matches. First there was the Tippman theory where they used a very large bore barrel and claimed that the air escaped evenly around the ball and it floated down the barrel without touching anything. They claimed this was the "air bearing effect". Next there was the tight barrel theory that said if the ball seals all the way around the shot will be more accurate. Actual testing has proven both these theories false.

Why match paint to barrel? Going back in time the paintballs were much more inconsistent than they are now, in fact now they are really, REALLY round and half the price. Players found that their consistency/accuracy improved when they used certain size barrels. Unfortunately paint is constantly changing size and this requires different barrel id's to work well.

The technique used to research paint/barrel match is simple and doable by anyone. Testing is performed by blowing a thin powder down the barrel to coat the inside.  Once you have coated the barrel you dry fire the gun once to clear out any extra powder. Lastly shoot one paintball out the gun and inspect the inside of the barrel. The powder will be stripped away everywhere the ball touched. This allows you to see exactly what happened to the ball down the barrel.

If the barrel is too big, the ball ricochets back and forth down the tube. We used to say it looked like Zebra stripes in there. Hence big barrels do NOT create an "air bearing". Barrels that are too small scrape most of the powder off and this creates excessive FRICTION. Tighter barrels that were too long were found to slow the balls down due to this friction. In other words, when you cut these barrels down, velocity went up. Remember the 8-10" acceleration distance, these barrels were 14" long and unported.

The best paint barrel match left two 1/8" wide streaks opposite each other down the barrel. The widest part of a paintball is usually the seam. With a proper size match only the balls seam touches the barrel snugly on two points. So what is happening here that makes this so desirable? We all know paintballs vary in size, this means that there will be slightly more or less friction on the ball depending on how tightly it fits in the barrel. If you use too tight a bore that touches the ball all around, trying to squeeze a bigger ball in greatly increases the friction and changes your velocity. By having the barrel sized to only touch two points, bigger or smaller balls only increase the contact patch a small amount and this gives you better shot to shot CONSISTENCY. So large a bore solves the friction problem but you get back to the ricochet effect.

The way to match your inserts to the paint you are shooting in practical terms is as follows.... Take out all of your inserts and shoot  3 paintballs over the crono with each insert. The correct insert for the paint you are using is the one that gives you the highest velocity. You then adjust the velocity accordingly. This insert will also give you the best efficiency. Easy when you know how.

Can a barrel effect efficiency?

Yes, yes it can. How many times have you heared the conversation that goes something along the lines of. "We have the same paintball gun, but you get 3 pots and a hopper from a 3000psi fill and I get 5 pots and a hopper", the difference will be the barrel.

Barrels are only there to accelerate the ball from a standstill to 300 fps. In theory they also help with accuracy but that's another story. The ball goes through incredible acceleration on its way down the barrel. The balls acceleration rate is approx. 50,000 feet per second to get to 300 feet per second in 10 inches. The entire barrel travel time is about 6 thousandths of a second and this means the ball is seeing about 1500 G's when its getting pushed out the gun. Although this may sound incredible if someone out there would like to do the maths you will that this is right.

Air pressure behind the ball is what causes this acceleration to happen. This pressure varies between the different guns but is generally between 50 to 125 pounds per square inch at its peak. The air pressure peaks right when the ball starts moving down the barrel, after that, the ball moving down the barrel creates a bigger chamber so the pressure drops. This is why low pressure guns are a myth, in reality all guns shoot at considerably lower pressure than 200 psi.

Peak pressures above 150 psi tends to break balls down the barrel due to really high acceleration and G forces. If you don't have any way to control the peak pressure behind the ball, the only way you can change it is to go with lower pressure in the air chamber, hence low pressure guns.

It is simple to understand that the harder you push something the faster it will accelerate and get up to speed in a shorter distance. So what distance do we have to get the ball up to speed? The effective length of the barrel is from the balls position before it's fired, to the place in the barrel where the pressure gets released, This is usually at the first porting holes or the step in the barrel. Porting is there to release gas pressure!! You are effectively stopping the acceleration at the ports so your 14" barrel that is half full of holes only has an effective length of 7".

Now we understand that we need to limit the peak pressure behind the ball to keep it from blowing up, and that the pressure drops as the ball moves down the barrel. The next question we need to ask is, how far down the barrel does the ball have to go before the pressure gets to low to do anything useful? That answer is 8-10 inches. We know this from looking at the graphs. If your peak pressure is higher, say over 100 psi you can get away with a shorter barrel, if it's lower then you need a longer barrel.

So in summary, you need a certain pressure to fire the paintball out of the end of the barrel. The shorter the barrel, the higher the acceleration needed to take the paintball from 0 to 300fps in a short space. But, it also needs a higher pressure to accellerate the ball from 0 to 300fps down a long barrel. Think about it, as the ball travels down the barrel, the pressure behind the ball reduces, so more is needed for the longer the barrel. The higher the pressure, the more stress is placed on the paintball meaning there is a good chance of it bursting in the barrel, especially if you are using a brittle tournament paint. So the shorted the barrel and the longer the barrel, the higher pressure is needed. There is clearly a bell curve here. The perfect barrel is the one that takes the least pressure to give 300fps. This is around 7 inches, or the length of a standard barrel insert. So you see, they did think about things when making barrel inserts.

The above information is based on testing done by AGD and also info from talkpaintball.com forum.