any rifled barrels were made on the principle of rifled barrels used in real guns: put a corkscrew-type spin on the ball, aimed at increasing distance. it doesn't really work since paintballs are round, and real bullets taper to a point. so rifled barrels in paintball don't do much at all.

the flatline, on the other hand, uses centrifugal force ( because the barrel curves upward slightly) to impart backspin on the ball, and in a sense giving it lift, and therefore 100+ feet of flat trajectory. by flat i mean flat; no curve due to gravity at all. it's wierd when you first shoot a gun with a flatline, because the ball appears to float along, alot slower than it would through a normal barrel, but it's just an illusion. if you're on the recieving end, you know what i'm talking about...

kickinwing2010 wrote: Actually if you look back to the black powder days they began to increase accuracy by rifleing there barrels so I would have to imagin if it worked with a metal ball it will for with a paintball, considering the paint to bore match is perfect.

This discussion could get involved. I own a Flatline (actually two), an Apex and a Hammerhead Pro. You are correct about the paint match to the bore. I used to be able to find paint that was large enough to touch the bore (.693"). With any paint and the correct sized back (Hammerhead calls them Fins) the barrel was very accurate (8" groups at 120 ft). But when I found paint that actually fit the bore...have to push it the entire length of the bore...accuracy was as good as 3" groups at 120ft.

Accuracy is almost unbelievable with that kind of paint to bore match. I used to get into big-time arguments on pbnation with the opposition claiming that liquid filled paintballs could not be spun. Finally I prevailed by pointing out that if spinning a ball was impossible then a Flatline could not work either...but we all know it does. And I'll say definitively that a paintball coming out of a barrel that actually imparts axial spin has improved accuracy just like the Kentucky rifle improved the accuracy of the mini-ball.

But, I have not found that there is any appreciable change in air time and distance of a paintball coming out of a rifled barrel. And, I cannot find any paint that actually continuously specs .693"-.694" so the full accuracy potential is moot. I have found a couple of "off brand" that measured that large, but the second time I bought them, both sized smaller.

At the chance of being redundant, the Flatline and Apex barrels have both proved themselves on the field and on the test range. Both impart backspin which generates lift and dramatically extends the flight and effective range of the ball. Accuracy "appears" to suffer at extended range, but my tests show that that is directly related to the fact that air currents have a longer time to act on the ball at such long flight time.

The Apex is not as finicky as the Flatline is as to the kind and size of paint you run through it. I find the Apex slightly more accurate than the Flatline, but when the Flatline is carefully adjusted with a good paint selection it is hard to really find any difference.

I loved the Flatline. I prefer the Apex and I use the Hammerhead, even when using small paint, more than the Apex on the speedball field.

Now, what would "straight" rifling do for a paintball?

I have seen several videos of tests on spiral ported barrels and they do not/can not impart spin.

Now all those fluid dynamicists may theorize on the ineffectiveness of spiral rifling on paintballs, but their theory falls apart when when you apply the same question about backspin.

Fact is few to none of the rifled barrels can actually impart axial spin to the paintball because the fit is not tight enough.

You can do your own test. Create a tight fit by cutting a small circular piece of tissue paper or paper napkin...or even a piece of "T" shirt material and use it to create a snug fit. Place the paper over the muzzle and push it into the bore of the rifled barrel with your finger tip to shape it. Pull it back out, place a paintball in the center and gently push it back down the bore with your finger tip. You now have essentially a "patched" ball (a black powder term) started down the bore. It should be a tight enough fit for you to feel resistance as the patched ball is pushed down the bore. Too tight and the ball may break when the marker is fired.

Use a bore fitting dowel to push the ball down the barrel until it rests against the end of the bolt. The ball will be spun by the rifling when it is fired. If you kept the patch small enough so that it doesn't wrap any further up the sides of the ball than is necessary to make a tight fit, when the ball is fired, the patch falls away just beyond the muzzle...so flight of the ball is not effected.

You may have to play with paper thickness and different ball sizes to get the needed fit. Good quality fresh paint is essential. You want uniform paint so there is no out-of-balance factor to skew the test.

Shoot twenty shots this way off of a bench rest with some kind of sight to assure repeatability of point of aim.

Then try the test with your good quality smooth bore with normal fitting paint.

My initial tests with the Hammerhead Pro was done this way and showed me that by getting a fit that assured axial spin, the barrel showed significantly better accuracy over a standard smooth bore.

Since "patching"each shot is certainly impossible during play, one would have to find a paint diameter that actually fit and touched the lans of the rifling on the full circumference of the ball.

RavenGuard wrote: *cough* paintballs are filled with liquid, which doesn't necessarily spin with the outer shell.  the effect may still be there, just likely too small to notice. also, a metal slug weighs more than a paintball, and the heavier a projectile the more accurate it will be at longer ranges.

So you are saying that my 243 caliber rifle cannot be as accurate as my 45-70? There is some accuracy retention due to weight of the projectile and its interaction with cross winds, but that is of little significance here. At extreme distance accuracy is reduced due to interaction with wind currents...just as with long distance travel of a paintball. Behavior of a bullet shot at a target 1000 yards away will have similar behavior over that distance as a paintball  does over a 200 foot distance.

If the THICK liquid core did not accelerate up to spin speed fairly well then neither the Flatline nor the Apex would work. Realize that the paintball in the Apex barrel goes from "0" rotation to fully functional backspin in less than 2 inches. So clearly the liquid core comes up to speed well enough to maintain the required backspin of the ball as it travels down field. That performance clearly indicates that the ball can be accelerated by rifling to its functional axial rotation in the length of a marker barrel. And the FACT is that I have done the tests as I described above and the axial spinning paintball is more accurate.

Ken and Bruce both have good points to their "Discussion" , and I think factoring in the relativeness of subjects like fluid dynamics , physics , ballistics and aerodynamics all have a great impact of the flight of a paintball , the other examples cited were just that , examples for illustration's sake .

First off , points of agreement :

The Flatline (and apex) barrel does extend flat flight through imparting a backspin on a paintball .

Paintballs , while not solidly filled , have very thick liquid , spin CAN be put on them ,or a flatline/apex wouldnt work .

Paintballs are round , roughly the same weight , and by all accounts , not perfectly round,,,, not a good aerodynamic design , but the first musket and blackpowder projectiles were also round . (and patched )

I am assuming that most readers of this thread have at least a passing familiarity with Physics , aerodynamics , and ballistics .

and remember !! everything said is as how it relates and affects the PAINTBALL in flight !

Imparting spin on a paintball gives it a couple of dynamic features that affect its flight , I am surprised nobody mentioned the Gyroscopic effects on stability any rotation will have on a paintball . Try getting a bicycle tire spinning as fast as you can , and then grabbing it by its axis of rotation and attempt to change the axis of rotation . point is this is called Axial rotation and is a great factor in stability of a projectile . the normal rifling twist in a .243 barrel is 1in24 (if I remember correctly) thats a relatively tight spin compared to other smokeless rounds . Physics says that ANY object exhibiting spin along it axis of movement will tend to display stability along that axis of rotation , wether its a bicycle tire , a musket round ,or a paintball . what will make that object more or less stable is the rate of spin over some definite distance , as mentioned in the .243 barrel rifling mentioned above . No doubt a .243 has more rotational spin , but then nobody needs to shoot much past 150 feet with a paintball .  conical rounds are more aerodynamically stable in flight because they have a higher proportion of weight to length along their axis of rotation , and they creat less drag with a pointed nose than a round one , but we're currently stuck with round paintballs , so there's not much we can do to change the aerodynamics of a paintball except put spin on it.(paintball velocities are for purposes of practical discussion within a very narrow window of 250 to 300 FPS, can we assume velocity will remain relatively constant at whatever value ?)

Aerodynamics ; the backspin of an Apex or Flatline does work , so we can assume the liquid inside the paintball does also spin , maybe not completely (and this may cause the paintball to lose its axial stability after a second or two , but by then gravity will have made it fall into the ground ) "Longballing" is 150 -175 feet anyway ...

Interesting fact , if a paintball and a rifled slug are shot at the same instant , they WILL fall to the ground at the same time if shot level on flat ground . Ya cant fool gravity , but by giving a paintball a little backspin , you creat an aerodynamic effect of "Lift" to offset gravity's effects for a very short time .

Tallen's description of an "Off-balance" paintball is true I've seen paintballs shot through a clean barrel actually "corkscrew" their way down the field , and I think everyone has seen "Flyers" that almost seem like they are more related to a boomerang than a paintball . This is caused by a spin that is NOT on the same axis as that of the barrel from which it was fired .

So far the velocity of a paintball has been discussed as it leaves the barrel , and this is great , in so far as it goes , but as soon as a paintball leaves the barrel , drag begins to slow it down , this is where errant breezes will begin to have an effect on its flight , the further out a paintball goes , the slower it goes and the greater chance for it being blown off course are assuming a wind thats tangent to its flight . Now,,, you put a Ballistic spin on a paintball (one that is a result of "Rifling" or other means of imparting an axial spin that is parallel to the barrel it is fired from ) aerodynamics and gyroscopic effects WILL have something to say about how stable its flight path will be . The same physical laws of aerodynamics that most everyone agrees works with the Apex and Flatline will minimize any tangental winds effects will have , in fact it will also tend to equalize the turbulent flow of air past the "Front" of the paintball while the ball is spinning . (but not in any significant manner) .

I have to point out , where the Flatline and Apex barrels really shine in use is when there is overhanging branches / brush in the way not allowing for a clear shot anyother way , they were designed not to really shoot any farther than a regular barrel , but to eliminate the ballistic arch for longish shots we all like to try ,,, they will shoot flatter for a distance , but drag will slow down (and gravity will pull down ) a shot from any barrel the same , apex , Flatline , or any good conventional barrel .  another unavoidable law of physics . True , somebody's gonna say , "But you just said above that backspin counteracted gravity !?!" , and it does for a very brief period of time . 

For discussion of what I'm about to bring up , backspin doesnt have any effect tho,,,  Impact energy , the amount of force it would take to break a paintball upon an intended target ,,, is determined by mass of projectile , density of said target (Facemask , or baggy sweatshirt ??) , shell of paintball (can we assume its the same for all paintballs , even tho we know its not ?) and velocity of paintball . All of these factors greatly influence the "Effective Range" of a paintball , what good is getting as paintball out to your target if there's not enough velocity left to break the shell when it gets there ? It'll bounce unless you're really lucky and there arent any of the factors that using side by side comparisons of Flatlines , Apex's and standard barrels , that we can alter to increase that "Effective range" ,,, Drag and gravity kill most hopes of getting anything but a lucky shot in much past , what ,,,,150-175 feet ?

Point is ,, anything you can do to make a ball fly more consistently is ultimately going to make it more "accurate" . Flatlines work , as do Apex (I might just get one of those tips for my cocker) , and so will giving a "Rifling-like" spin to a paintball , I can see where it would make it extremely accurate in fact...

BUT !! would doing it be convenient NO !! (as Bruce pointed out) , would it be fast ? , No,,  With current paintball technology its not really practical (I think Bruce alluded to that too ) , but it can be done .

 Hmm , patching a paintball and playing "Civil war"  , Dang , we already play civil war rules at my field sometimes,,, One shot , hand loaded , no hoppers..

Very well said Shadow. I think you hit all the points. I have alluded to all of them in various posts and to some extensive accuracy testing I did last year in a warehouse.

Now competition with single shot muzzle loaded patched paintballs in rifled barrels...floppy brimmed hats and exposed hammers. Sounds like an experience...Wait, in that case you could make a paint "ball" that is cylindrical with rounded ends. Son of a gun, that would look like a boat-tail bullet. I can see it now, long range competition with windage flags and spotting scopes with the traps set all the way out to 1500............inches (about 125 ft).

Divine , my brain hurts too .

 We are dealing with a subject that involves many variables , even from shot to shot with exactly the same marker , paint and power source .

I think all of the information brought to light can best be digested as an approximation . The higher mathematics can be left for engineers and astrophysicists . paintball isnt an exercise in either , but an  awareness of these things makes paintball interesting .

Amen ,,, I've shot a .45 calibre Parker Hale black powder that was the sniper rifle of the south during the Civil war . many confirmed kills at 1500 yards and beyond , does that information or experience relate to paintball ? NOT !!  but the awareness of the laws that govern objects in motion does . Nuff said .

Let this one die .

OOPS did I say Sniper ?

aGUYnamedLARRY wrote: I think this whoooooole  stupid mess is ..... stupid. I think that if people wanna know what's more accurate they should go and try it for themselves.  And if you haven't shot a rifled barrel,  don't go preachin  that it's  the worst thing ever AND,   if you haven't got sufficient data,  don't go preaching that it's the best thing ever. The best judgment for these things is actual,  on field experience with both types of barrel.   I have neither,  but I'm sure someone on this sight does.   If you don't believe him,  go try it out for yourself.

I have that field experience, which is at best empirical and not a controlled test,  and many hours of extensive testing where as many variables as possible were removed (markers set in sand bags rather than hand held...paint that is measured for size and roundness and regulated air supplies, just to cover a few of the protocols followed). Much about those tests brought conclusions that I have posted in these forums. Those results are given short shrift by many who don't want to be confused by the facts. I own, have owned or have access to all the barrels about which I appraise accuracy and range.

BTW, THE most accurate barrel I have ever tested was a long (17 inch) smooth bore that gets tighter towards the muzzle...to the point that the paintballs will not drop through. No other, out of the box, barrel shoots as well as this apparently discontinued barrel.