So what exactly does a barrel do? Basically it acts as a type of expansion chamber. A blast of compressed gas hits the breach and starts expanding behind the paintball. The expansion rate of any gas is determined largely by the composition and initial pressure of the gas. The composition of the gas with respect to paintball pretty much means whether you're using CO2 or highly compressed air ( HPA. ) CO2 is heavier than normal air and also expands just a little slower.
Initial pressure is a little more complex. As this guide is on barrels, I don't wish to get into the mechanics of different marker designs or how the gas gets to the barrel breach. Suffice to say different marker designs ( blowback, spool valve, etc, ) have different operating pressure requirements ranging from just above 100 psi to 800 psi. The higher the pressure the faster it will expand meaning a larger force behind the paintball and a faster acceleration inside the barrel. Just keep in mind that even if a marker runs at a high pressure, like most Spyders and Tippmanns, that doesn't mean all the air is used to shoot the ball. Most higher pressure designs are a form of blowback so some of that gas is used to cycle the marker action. If you take your basic inline blowback, like a 98C or Stingray, the hammer opens the valve which vents ~800 psi into the marker internals. This gas immediately starts expanding, pushing the hammer back on one end and venting down the power tube on the other. By the time the air even reaches the paintball in the chamber it is at a significantly lower pressure then when it left the valve. With that said, the ball is usually getting hit harder than an electro marker running at 160 psi.
I'll go more into this pressure difference later, but right now let's continue onto the actual firing sequence. As you should know, pressurized gasses seek equilibrium with their surroundings and the easiest way to escape is of course down the barrel. The force of the expanding gas easily overcomes the friction between the paintball and the barrel so the paintball goes for a ride. So long as the gas is expanding directly into the ball ( in that it has no where else to go, ) it will continue to accelerate. And this is where porting and steppes come into play.
The little holes drilled in the sides of barrels, usually toward the front, are called ports, collectively porting. They are meant to vent air from the inside of the barrel to the outside. This happens at two points. First air in front of the ball when being fired can more easily escape rather than being gathered in front of it and forced out the muzzle. Next it also lets some of the gas behind the ball slowly bleed off. Since the gas can vent slower over a larger area the sound signature is more like a "phoomf" instead of a loud "POP." However, in letting some of the gas release, you lose pressure behind the ball before it has left the muzzle. Now theoretically this means that if all the shot pressure vents before the ball exits the muzzle then it will slow down a bit while still in the barrel as it's facing normal wind resistance. But consider that the ball is moving 240 fps or more by the time porting kicks in and so it can pass more than 12" of porting in less than 5 milliseconds. It would take a great deal of porting and an insanely long barrel to have the ball slow down enough to face any adverse conditions, like rolling along the barrel bottom as gravity pulled it down.
Many barrels also have a steppe inside as well. A steppe is a sudden increase in the bore size. This usually happens about where the porting starts and helps the venting as the ball is no longer directly touching the barrel walls. If you look down a barrel from the muzzle end ( please remove it from you marker first! ) you will see a little ring, that's the steppe. If you look from the breach end you likely won't see it.
High & Low Pressure Markers
So you may ask why both a low pressure electro and high pressure blowback are firing paintballs at the same velocity. I will admit I don't have any concrete numbers or facts on this one. Here's my take. It's all about the power of the gas expansion, the rate of the work being done. In a low pressure marker, the gas is expanding slower and the paintball is getting a nice gentle ride down the barrel. By the time the paintball reaches the muzzle nearly all the energy in the gas has been expended, it doesn't waste energy in the gas. Have you ever noticed that low pressure markers are so much quieter than high pressure ones? This is because the gas vented after each shot is lower in volume and also traveling much slower so the compression waves ( sound ) made are much weaker. Also, have you ever seen a snub barrel on a low pressure marker? I'm not saying it can't be done, but I've never seen it. With such a short travel distance I don't think the low pressure gas has enough time to accelerate the ball to playable speeds.
High pressure markers are much more violent with paint. They hit the ball harder and accelerate it faster down the barrel. When the ball hits the porting the gas behind it still has a lot of energy to give but it gets wasted as it's vented out. Conversely as mentioned above the louder sound signature comes from the larger volume of high pressure gas slamming into the relatively calm air around the marker. As I said, I don't have full proof of this and as such I more than welcome anyone who can give me me solid info to the contrary.
Now some may argue that hitting a paintball with higher pressures can warp it, potentially throwing off accuracy as a lopsided paintball will fly erratically compared to a perfect sphere. Theoretically there is some truth to this. Have you ever seen those slow motion physics videos in school where a baseball partially wraps around the bat when it gets hit, or a golf ball flattening against a club? However gasses expand uniformly meaning that the paintball is getting pushed across the whole backside of it instead of just on a single point. Upon the initial blast, yes the very back of the paintball gets the brunt, but the pressure equalizes quickly. The gelatin will usually just snap back into shape. Any air blast strong enough to permanently deform a paintball will just as likely break it in the barrel. Indeed many high pressure markers have difficulty firing thin shell paint because the blast is just too much for the shell to take.
Bore Matching & Paint Quality
So you may have known everything mentioned above, but what's this about paint to bore matching everyone keeps talking about? First, if you don't already know, the bore is the distance between the insides of the barrel wall, the inner diameter. Conversely the bore of ammo is the distance between the outside edges, the outer diameter. Even though a standard paintball is supposed to be .68 caliber they actually can vary between .679 and .695. Most balls stay in the range of .684 - .691 though. Here's a rather good chart matching average ball sizes to common paint brands. So what does this mean for you the player? Well, mainly it concerns your barrel, its bore size, and the size of your ammunition.
As mentioned above, the ball only gets accelerated when there's sufficient pressure behind it to overcome the friction between it and the barrel wall. Normally this isn't a problem because the friction is very low and the pressure is relatively high. But when the paintball doesn't fit right in the barrel bore. some very bad things can happen.
Firing small paint through a larger barrel can be done, but you have a larger gap between the ball and the barrel. This means you lose gas efficiency because gas that otherwise could be pushing the ball out is escaping around it. This means you have to turn up your air flow to get your muzzle velocity up where it needs to be. Accuracy is also affected because the ball will likely touch one side of the wall more than another and pick up some bad spin. In some cases the paintball can actually "pinball" down the barrel bouncing from one side to the other. You can read the Flatline / Apex section for an explanation on spin.
Trying to fire large paint through small barrels is usually worse. The gelatin shell of a paintball is flexible so it can probably squeeze in, but the ball is being put under excess pressure and stress. Combine this with the extra friction as it tries to slide down the barrel and often the shell will just fall apart inside the barrel. This is commonly known as a "break." If you've ever fired a shot only to see goo spray out of the muzzle, this is what I'm talking about.
Ideally the paint should just touch the barrel walls on two or three points. No paint shell is perfectly spherical so it won't be a perfect seal all the way around. If the paint can roll out on its own then it's too small for the barrel. You should be able to blow it out of the barrel with a light puff of air. Many players think it needs to be too tight, I know I did at first as well. Also you may need to perform a size test throughout a day of play. As temperatures and humidity rise from morning to afternoon it's not uncommon for paint to swell a little bit.
But even with a proper bore match, you will get poor results if using low grade paint. So what exactly constitutes quality paint? First check the shape. As stated above no paintball will be perfectly spherical, but the bad stuff will be somewhat lopsided or otherwise poorly formed. Along with the shape, look at the shell construction. Particularly note the seams between the two halves. The smoother and less noticeable they are the better. Pronounced seams can rub badly in a barrel and against the air when fired. This usually results in "flyaway" shots. Next toss some paintballs in the air with a little spin. If you see them wobble while spinning that means the ball is unbalanced. This can be from voids and bubbles in the paint fill or uneven shell thickness. Examine the shell itself, the color will likely be more or less translucent where the thickness changes. The seams will almost always be a little thicker than the rest and this is normal. Either problem is a mark of poorly made paintball. Finally look at the size. Again, not all paintballs are exactly the same size but each brand and type should have a tight tolerance range for size variances. when performing the bore test listed above make sure you test a handful of balls not just one or two. If they all match the bore about the same then most the balls in the bag/case should be about the same size too. If you've got a couple that are noticeably larger or smaller than the others grab a few more from the bag/case and test those. If you continue to have noticeable size variances you may want to steer clear from that paint in the future.
The above are ways to find quality paintball brands and types, but that doesn't cover what is best for you as a player. You need to consider your shooting habits as well as the quality of the paint. If you tend to lay a lot of fire for suppression purposes then you're usually more worried about simply laying paint downfield and not so much as to putting it right on target. With this in mind having the occasional flyaway shot may not matter to you. In this case you may opt to go for some cheaper paint in the middle to low grade category since you'll be shooting so much more of it. However if you're picky with you shots and don't shoot a whole lot during a match then you likely want the most consistent paint you can get. This might call for some premium paint, but since you shoot less of it you can afford to pay the higher prices per case.
Finally some paint is designed for specific situations. Some paint is specially made for cold and harsh weather by having a particularly thick shell or specially formulated paint inside. As the gelatin shell gets colder it becomes more brittle and will break instead of just bending. A thicker shell makes it a little tougher to endure the elements better. However the thicker shell can make it tougher to break on impact resulting in some shots bouncing off the target. This isn't a given but it can happen from time to time, particularly in warmer weather. On the other end of the spectrum is the thin shelled paint. This is often referred to as "tourney" or speedball paint since the weak shell will break easier upon impact negating the chance of bouncing off a hit target. This type of ammo is often premium grade but be careful before stocking up on it. Remember that high pressure markers are harder on paint. Mixing the two usually results in a lot of broken balls in the barrel since the weak shell can't withstand the higher pressure. Also as the temperature drops this paint becomes even easier to break.
With all this in mind you should be ready to find the best paint for your particular situation. But what about picking the right barrel? Well, now that we've discussed the basics of what happens inside the barrel and the way it interacts with paint it's time to get into some details and factors that greatly affect how each barrel can perform very differently depending on the situation.
Kit or Not?
What exactly is a barrel kit? A kit is a system that allows the barrel bore to be increased or decreased. This is usually done with either two or three piece barrels. Two piece barrels have a back and front the attach in the middle. The entire kit usually has a selection of back pieces, each of which have a different bore size, that can be attached to the front and then used as a full barrel. Three piece kits usually involve a single large bore back piece that holds sleeves or inserts to adjust the bore size. The front portion still attaches to the back to complete the barrel. While the back pieces are usually all the same, save different bore sizes, the fronts usually come in many varieties of lengths, porting patterns, and looks. The fronts are almost always much larger than any of the backs, around .700 bore size. This is just like the steppe found in many one piece barrels meaning the front of a kit is not used
The largest benefit of a kit is it allows you to change the inside bore of a barrel to match the paint you're using. Usually you can't always guarantee what ammo you use. Some fields enforce a field paint only ( FPO ) rule where you have to buy ammo from them and you don't know if they're always carrying the same stuff. Or maybe during a long say of play your paint has swollen a bit. In situations like this it's very helpful to have the option of adapting your barrel to the paint rather than just making due with a single bore.
Another option is the elliptical barrel. Instead of being a straight pipe the inside gradually flares just ahead of the breach then closes in again as it approaches the muzzle. These are often called progressive, elliptical, or parabolic barrels. The Palmer's brass barrel is one of the most well known examples of this. The manufacturers of such barrels claim the elliptical honing allows for the slight expansion and deformation a paintball goes through when first hit by the blast of high pressure gas. In effect it's supposed to give a quasi-kit effect in matching the bore to the paintball. I admit haven't had any firsthand experience with these types of designs so I can't comment on this "authoritatively." However from the numerous remarks from friends that do have such barrels, I'm inclined to believe they do live up to at least some of the hype. If the claims about the paintball warping is true I'd also be led to believe these will function better in higher pressure markers.
Picking a Length
With barrel bores, kits, and paintballs covered, next it's time to pick a barrel length. And inevitably the question will arise, "Which length is best?" And again the answer will be, "It depends on your preferences." Generally barrels can be grouped into three length categories: short, medium, and long.
Snub barrels, those 6" and under, are a popular choice for those people going for a mil-sim, close-quarter battle ( CQB, ) look. The compact size makes them very maneuverable and easy to use without worry of hanging up in the brush, catching on trees, etc. On the downside they can be gas hogs too. The shorter distance requires the ball to reach maximum velocity in a much shorter time, requiring a larger blast of air. Again this can potentially translate to more balls broken inside the barrel when using more delicate paint. Most snub barrels lack any porting or steppes and this combined with the higher gas usage means they tend to be very loud. The shorter length also means the barrel will have less time to fully control the ball meaning that some accuracy may be sacrificed, but this isn't always a given. The last thing to consider about this category is it gives you little to work with when trying to poke past brush and bunkers.
Medium length barrels, those between 8" and 14", are more likely than not going to be the best all around things for the average player. They usually have ample but not overdone porting to help lower your sound signature a little while not overly venting gas, yielding decent air efficiency. Bunker walls and brush can be pushed aside easily enough but you won't find it too clumsy elsewhere. Not surprisingly this is where you'll find the most options for barrels.
A long barrel, anything about 14" and over, functions pretty much the same as one of medium length, they usually just have more porting. This extra porting helps in quieting the barrel a little more. The extra length can also help in shooting through brush or clearing aside bunkers. The downside is that longer barrels can be unwieldy in rough terrain. They can get caught up in bushes, smacked on trees, or get dug in the ground when crouching down. If you opt for one you may have to adjust the way you carry your marker.
Long barrels often have two myths associated with them. Many new players believe they are more accurate than shorter counterparts. Longer barrels help accuracy in firearms by one, giving a longer control time on the bullet, and two, allowing the explosive charge a longer time to accelerate the bullet yielding a faster muzzle velocity and flatter trajectory to the target. However paintball barrels have neither of these properties. First, regulated paintball fields have a muzzle velocity limit so all players will have similar ballistic trajectories. Second most marker barrels have porting and a steppe meaning the controlled bore section is 6" - 10" at most. Even if you were to use a full length non-stepped, non-ported barrel paintballs don't gain any additional stability past 10"' of control.
The second myth with long barrels is that they have much higher gas requirements. This one can go both ways depending on the barrel design but generally it's false. As mentioned above, most of the time a steppe and/or porting will kick in after 10" at most and so they function much the same as an average length barrel. Theoretically it's actually possible to get better gas efficiency out of a longer barrel. The longer the control section the longer the paintball has to be accelerated meaning you can get more work out of less gas. The myth that they use more gas arises from the extensive porting which many people think allows excess gas venting and friction pulling the ball back. The only way this myth would be true is if you have some archaic barrel with an non-stepped porting section ( I personally don't know of any. ) In this case, yes the ball is no longer being pushed once it reaches the porting but it still faces the friction with the barrel walls. You would then have to use more gas to accelerate the ball over normal velocity limits so that after it slows down in the porting it's traveling at normal speeds. However on nearly all barrels in this day the ball is no longer even touching the barrel at that point so any friction is from wind resistance alone. Also as mentioned above at 240 fps a paintball can pass 12" of porting in less than 5 milliseconds. In that time the ball will drop less than 0.0096" meaning it's almost impossible for it to start rolling along the barrel bottom before it exits the muzzle.
So, what makes two barrels of the same length and bore different in terms of quality? Well, it boils down to how they change the ballistics of a paintball's flight. Barrels should ideally be completely smooth on the inside ( I won't get into rifled barrels here. ) This allows the ball to slide down the barrel without picking up any adverse spin on them. The smoother the barrel, ( as well as straighter, though it shouldn't be an issue, ) the better. Since not every paintball contacts the barrel walls in the same way, even uniform roughness can impart drastically different spins on each shot. This is further exaggerated when using low quality paint with heavy seams, dimples, voids, etc. Barrels like the Flatline and Apex try to control spin and use this to their benefit ( more on that below. ) The material of the barrel also matters. Most barrels now are aluminum with some being brass, steel, and now carbon fiber. Many people love brass because it has a low coefficient of friction. That means less friction on balls as they slide down it. Aluminum is nice since it has little weight. Steel of course is really durable. Carbon fiber is also incredibly durable but has the added benefit of being extremely light. It also doesn't expand or contract with temperature so the bore size stays perfectly constant in warm or cold weather play, unlike metal which fluctuates ever so slightly. It also has a muffling effect on the sound signature of the marker acting like a mild silencer. You may hear a lot about J&J barrels as well. These have a ceramic and Teflon coating on them which makes them particularly slick on the inside. The benefit here is that paint doesn't adhere so the paint residue left from a ball breaking in the barrel is more easily flushed out with one or two following shots.
Flatline / Apex
The Flatline has an "S" curve to it that forces a ball to roll along the top as it is fired. This gives the ball backspin like a baseball pitcher's fastball. As it flies through the air the backspin will cause a pocket of higher pressure air to form below it. This gives the ball some lift as it flies yielding an increased shot range. However, this spin is a tricky thing to control. If you've ever heard people asking for the best combination of paint to velocity in a Flatline, it's because they're trying to find the best balance between backspin and forward velocity. The amount of lift the ball experiences is directly proportional to the spin rate. Basically more spin means more lift. Too little spin means the ball will go a little farther, but not much. Too much spin and the ball will actually curve upward, die, then drop nearly straight down, much like a golf ball when hit by a middle iron or high driver club. When it's just right the ball follows a very flat trajectory with a greater overall distance. The Apex also uses spin in attempt to control the shot, but with a different system. Instead of rolling along a barrel wall the Apex can be attached to most any barrel muzzle. Inside it has an adjustable fin that makes contact with the ball as it leaves the barrel muzzle and imparts spin there. It can also be rotated around to give sidespin as well as topspin if you want to try pulling off trick shots like curving around corners or dropping over bunker walls. However, since both of these barrels rely on making significant contact with the paintball, they will handle each ball slightly different just as every ball is slightly different. This generally translates to less consistent shooting, especially at long ranges. It's doubt you'd notice any detriment at normal engagement ranges, but after about 60' you'll see balls starting to veer off. Both these systems can also be harsh on paint so you would do best to steer away from brittle shells. Another thing to keep in mind is that you want to keep your marker as close to vertical as possible when firing ( for the Flatline in any case. ) Otherwise the ball will have a touch of side spin on it as it exits which will make the ball curve to one side or the other.
After asking about accuracy this is usually the second question about barrels. In the sport of paintball maximum range is determined by ballistics after the paintball leaves the barrel. You fire a paintball at a set maximum field velocity, so regardless how it got to that velocity, as explained above, your barrel cannot affect the shot after it leaves the muzzle. After it's been fired ( assuming it doesn't hit any obstacle before the ground, ) trajectory, momentum, and wind resistance are the only factors that matter. Obviously if you fire your marker upward, you can get the ball to go farther so I won't touch on that. Now on a windy day, cross winds will blow you shots off course, head winds will slow them down, tail winds will carry them farther, etc. Again that's not something I need comment on. The only thing left is momentum, that wonderful physical property derived from mass x velocity. Now, we already know velocity is, or should be, constant. So that leaves mass, something that fluctuates with each paintball. We know paintballs differ in size and weight. Heavier paintballs have greater momentum and will be able to resist change from the air better. Also smaller paintballs give less surface area for the wind to push against so that also helps to resist wind change. So assuming paintballs are perfect spheres ( no seams, dimples, or lopsided balls, ) the densest paintballs ( greatest weight in the smallest package, ) should fly the best. Even then you're talking about a couple feet difference so is it really worth it to research which brand and type of ammo is the densest? But all that happens after the ball leaves the muzzle. So regardless of whether you have a "rifle" or pistol, HPA, CO2, or whatever, the range of any standard barrel is all the same
I've heard lots of wild stories about barrels, but for some reason this one seems to be repeated quite often. To anyone who thinks in-barrel ball collisions can happen in any barrel, well they don't. I'm not saying it's impossible, just extremely improbable that such extreme conditions would occur. We're talking about an event where ball one hits some impediment(s) and slows down while ball two somehow ignores the same obstacle(s) to then catch up and collide with ball one, in a mere 14" - 20" distance no less. I mean physics can prove the Magic Bullet Theory so I guess this could be possible, but here in the normal universe . . .
So What's the Best?
So after all this blathering, what's the best barrel? Well that depends on what feels right to you, what's in your budget, and what company you want to support. I've got friends and acquaintances, some on teams, some pros, some rec players, that play a lot of paintball. They use J&J's, Hammerheads, Ultralites, Freaks, St!ffis, Empire, and just about anything else out there. They all say the same thing: so long as you have quality paint that matches the bore well, you won't see any appreciable difference. Your marker will also determine what length feels right to you. Inline blowback designs ( Tippmanns, Stingrays, some Spyders, etc ) generally tend to be longer markers while blow forwards ( AGD and Tiberius, ) and stacked tubes ( including many Spyders and most electros, ) are rather compact. I've actually measured it out and an A-5 with a 12" barrel is the same overall length as an AGD Tac One with an 18" barrel. So, when people give recommendations on barrel lengths, take into account what marker they already use. In the end so long as you have a proper paint to bore match, use a quality paint, and know how to properly aim your marker, you won't really see any appreciable difference between barrels of similar size.
In conclusion, class repeat after me:
"I hereby understand that the operation and use of paintball barrels is a complex operation with many variables. As such there is no end-all be-all barrel for every player of every situation. Barrel brand, length, and material are not the lone factors in accuracy nor air efficiency, it has absolutely nothing to do with range, and I will not spread fallacies to the contrary. I understand that many players can be confused by marketing hype, bad information, and baseless speculation and that at some point I was likely in this crowd. As such I vow to not mock, tease, or heckle such players but instead educate them that they may do the same for those around them." That will do.
As always, comments, thoughts, additions, and what not are appreciated.
This post has been edited by Jaron: 03 February 2008 - 09:30 PM