Marker barrels tend to be one of the most commonly debated topics. So let's see if we can shed a little light on this oft confused and misunderstood part of our equipment.


Paint to Bore Matching
First off, what's this about paint to bore match everyone keeps talking about? Well, even though a standard paintball is supposed to be .68 caliber they actually can vary between .679 and .695. Most stays 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 the player? Well, mainly it concerns your barrel and its bore size. Trying to fire paint that doesn't fit your bore size can have some very bad results.

Firing small paint through a larger barrel can be done, but you lose both air efficiency and accuracy. Air efficiency is lost because air 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. Accuracy is affected because the ball will likely touch one side of the wall more than another and pick up some spin.

Trying to fire large paint through small barrels is usually worse. The gelatin shell is flexible so it can probably squeeze in, but the ball is being put under excess pressure and stress. This usually results in breaking the ball, not chopping it. Chopping comes from misfeeds where the bolt or something else breaks the ball. Breaking a ball is when the ball itself is put under too much tension and bursts.

This is where a barrel kit comes in handy. It allows you to change the inside bore of a barrel to match the paint you're using. Sometimes you have to use random field paint only, sometimes your existing paint has swollen a touch from the weather, or whatever. Ideally the paintball should just touch the inside of the barrel at more than one place ( paint isn't perfectly spherical so it won't touch all around. ) It shouldn't just roll out, but anything to a light puff of air to just sliding through on its own is fine. Many people think the paint has to be tighter than it actually does, I know I did at first.


Range
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 ( I'll examine this below, ) your barrel cannot affect the shot after it leaves the muzzle. After it's been fired ( assuming it doesn't hit anything before the ground, ) trajectory, momentum, and wind resistance are the only factors that matter. Obviously if you fire your marker upwards, 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. But all that happens after the ball leaves the muzzle. So regardless of whether you have a "rifle" or pistol, HPA or CO2, the range is all the same. Now let's explore what happens inside the barrel.


Internal Action
Basically your barrel acts as an expansion chamber for a paintball. A blast of compressed air hits the breach and starts expanding. Now gas temperature does affect pressure, but realize that it's most likely passed through a regulator or two before getting to the valve so pressure should be fairly constant. If it's a cold day you'll just be using more air molecules to get the same pressure than on a hot day. Any variance on expansion speed due to weather will be negligible. Note, this is not the same as why CO2 loses pressure when cold or after rapid firing. That happens because the liquid has cooled to the point where it won't evaporate quickly enough to replenish the air supply.

Some people talk about about extra friction in longer barrels. That's not always the case. Many barrels are stepped or flared so that about the time the porting starts the bore expands either instantly or gradually ( usually to about .700 or larger, ) and the paintball is no longer even touching the walls ( this does allow gas to escape around the paintball a little, more on that below. ) This is especially true in two piece barrels. Look down your barrel both ways. From the breach you won't see anything. From the muzzle if you see a ring inside, that's the step. Any "friction" will be coming from wind turbulence. Before you fire, the air in your barrel is at a standstill so the paintball has to break through it. This isn't difficult since it has the continual force of an expanding gas behind it. But this is where porting comes into play.


Porting
Porting allows that air in front of the ball to more easily escape rather than being gathered in front of it and forced out the muzzle. It also lets some of the gas behind the ball slowly bleed off rather than escape all at once with a distinctive POP. However, in letting some of the gas release, you lose pressure behind the ball and it can start "free floating" or even leave a vacuum behind it before exiting the muzzle. Any barrel size with more than, say, 4" of porting will result in the ball noticeably slowing down before it leaves the barrel because rather than being pushed out, it's facing air and possibly barrel friction. The longer the porting, the more the slowdown.


High & Low Pressure Markers
Some people argue that range and accuracy between high pressure vs low pressure markers varies greatly. Here's something to think about on that. Most high pressure markers are built on some sort of recoil system where some of the gas used to fire the paintball is used to recock the marker. So even though a Tippmann runs on 850 psi, the ball is not getting hit with all the air. Some released gas drives the hammer back, which then goes on to feed the cyclone, etc. I'd like to have actual numbers on what percentage of the air actually expels the paintball, but I don't have it. However, it is getting a bigger hit than a low pressure electro marker. And yes, the higher the pressure that actually affects the ball does change the acceleration. This being the case, I don't think low pressure markers would do well with snub nose barrels. Why? Because the pressure needs time to expand to accelerate the paintball up to the desired velocity and higher pressure will be able to expand faster. So, if you're operating on 150 psi, you'd really have to crank up your output ( either up the pressure or keep the valve open longer, ) to get that ball up to speed in only a couple inches. Keep in mind however that as the gas expands it does lose pressure. Also, air impact does warp the ball slightly so hitting it harder does have the potential to throw your accuracy off a bit from having lopsided balls. Some manufacturers make progressive or parabolic barrels that are supposedly able to take this warp effect into consideration by having the barrel expand slightly just ahead of the breach then close in again as it approaches the muzzle so as to not break as many balls. These are often called progressive, elliptical, or parabolic barrels. Palmer's brass barrels also do this. I haven't had any firsthand experience with these types of designs so I honestly don't know if it helps that much.


Picking a Length
So, what does all this mean for barrels? Basically this. Snub barrels ( I'll say under 6" ) require extra gas pressure since they have a short distance to ramp the ball up to speed. They also tend to be louder since they don't have any porting. Also, they can be a little less accurate since that big hit of gas can deform the ball. However, you don't lose any gas pressing against the ball so you can never get that vacuum effect ( rare as it is anyway. ) They're also very quick and easy to use due to their compact size ( no digging them in the ground, hanging up in the brush, etc. )

Average length barrels ( I'll say 8" - 14" ) are more likely than not going to be the best all around things. They usually have ample ( but not overdone, ) porting to help lower your sound signature while not overly venting gas, yielding good over all air efficiency. They have enough length to push aside bunker walls and shoot through brush without being overly clumsy. Not surprisingly this is where you'll find the most options for barrels. Choosing a length here comes down to personal preference ( my 14" was a touch too clumsy so I opted for something in the 10" - 12" range, ) since there really isn't any significant performance difference.

Long barrels ( anything over 14" ) can be as much gas hogs as extremely short barrels, but that's mainly in unstepped barrels. This comes from the extensive porting. Just like all barrels, you have to get the ball up to ( or even over ) speed before the porting kicks in. The difference here is that snub barrels completely release the ball and average length barrels only have a couple inches at most for the ball to travel before it exits. Long barrels can have up to 10" or more of porting. During most of that time, the ball isn't getting pushed anymore. In an unstepped barrel, this results is friction pulling the ball back so you have to get the ball going well above field velocity before it leaves the barrel. In a stepped barrel, if the ball is traveling slow enough it's possible for gravity to pull the ball down enough where it starts riding along the bottom. This can pick up a slight topspin, resulting in shots that actually drop like a slider pitch, reducing maximum range. To counter both of these, you must hit the ball with more air so it can leave the muzzle at field velocity, which as mentioned before, suffers from potential ball deformation. So in some cases, long barrels can actually be less accurate than their small counterparts. On the upside, they're great for clearing bunkers and brush out of your view and are generally very quiet.


In-Barrel Collisions
To anyone who thinks in-barrel ball collisions can happen in longer barrels, 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.


Materials
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. Many stock barrels are still somewhat rough on the inside. 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 hardly any weight. 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 slightly. It also has a muffling effect on the sound signature of the marker acting like a mild silencer.


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. 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. Too little spin and 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 imparts spin to a ball, but rather than adjusting muzzle velocity, you can adjust the tip to control how much contact it has with the ball. It can also be rotated around to give sidespin as well as topspin if you want to try pulling off trick shots. 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. I doubt you'd notice any detriment at normal engagement ranges, but after about 60' you'll see balls starting to veer off. 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.


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 that play a lot of paintball. They use J&J's, Hammerheads, Ultralites, Freaks, St!ffis, Empire, and just about anything else out there. Your marker will also determine what length feels right to you. Inline blowback designs ( Tippmanns, Stingrays, most Spyders, etc ) generally tend to be longer markers while blow forwards ( AGD and Tiberius ) and 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.


EULA
In conclusion, class repeat after me:
"Barrel length is not the lone factor in accuracy nor air efficiency, it has absolutely nothing to do with range, and I will not spread fallacies to the contrary."

As always, comments, thoughts, additions, and what not are appreciated.

__________________
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- J
Paintball FAQ's | Asking yourself "What should I get next?" | Barrel Facts | Fixing the Chop
HPA vs. CO2 | Regulator FAQ's | To Remote or Not To Remote | Slide Checks 101 | LPK FAQ's
Which Vest is for Me? | Scopes vs. Red Dots | Rails, Sights, & Targeting

yay! one post up

Stickied

sweet!
thanks

sweet post, it will come in handy

Note to all.
the bore size of the Flatline barrel is .700
this is to leave enough room around the paintball to allow air to pass around it to give it it's necessary spin.

What about brass!?!

you use brass, you tell me.
I don't know brass yet

No not that, I meant about Jaron's write-up.

Brass bore sizes are either .685 or .690..

ahhhh
palmers brass size confirmed
.685 and .690
not to down you pizza.
I found that right after you posted.