Do Barrels Truly Affect Accuracy?

  – Hoot

With our recent Lapco sponsorship, I have really began to look into the accuracy of barrels, so that I would make a wise decision in choosing my free barrel. I know Taylor has posted some extensive testing results on various barrels awhile back. Do you have the link to that again Taylor?

I’ve been digging, looking at the differences between underboring vs overboring vs bore match (blow test), re-examined barrel lengths, etc. These are the results I have been finding:

The conclusions I have been seeing (from the legit tests) show that paintballs are getting smaller (as most of us are aware). 5-7 years ago every paintball was around .689. Now pballs are sitting at .682-.685 on the average (before swelling in humidity).

Paintballs are being made smaller.

Another fact: barrel Lengths have relatively nothing to do with accuracy. The PunkWorks tests (very good tests) two most accurate barrels were 21″ and 10″ barrels. In essence, the longest and shortest barrel they tested.  The marker used was locked into a vice to create a reliable testing platform. So length means little from a mechanical standpoint (past the initial 4″). HOWEVER, something the tests do not account for is the user. Semi-long barrels, such as a 12″-14″ provides the user with a longer sight plain. Example: when you go clay shooting with a shotgun, I have tried to shoot clays with my short home defense shotgun (very short barrel length) and my longer hunting shotgun (longer barrel length). I hit a lot more clays with the longer barrel. Why, because it’s more accurate? Not really. It’s because my sight plain is longer. I am able to follow the barrel to the target easier and track it. This applies to those who use the top of the marker for a sight plain, or those who use the side of the marker for sight plain. The trick is finding the right balance though. Too long of a barrel becomes awkward and counter-productive when trying to manuever. But a medium sized barrel such as a 12-14″ provides a user with the longer sight plain, and still easy to manipulate in our hands.

Barrel Length means almost nothing in terms of mechanical accuracy. However, barrel length affects user accuracy.

The inner circular exactness of the barrel is key (which Lapco boasts about), along with bore size. But initial conclusions I am seeing show that bore size affects accuracy different than I imagined.

Ultimately “Vortex Shedding” that happens around the pball in flight is what causes your greatest difference in accuracy. If your shell is not truly circular, you get random pressure changes behind the ball = random forces pushing the shell off course. If your shell is completely circular, your pressure changes ie forces behind the ball would be almost exactly the same each time, hence the ball stays on the same course. Thus, really good shells improve accuracy, however, even the best pballs are not exactly circular.

Really good paintballs, those consistenly shaped the same, increase accuracy.

Bore Size comes into play to utilize the air being used in a more consistent/effecient way. Underboring and bore match will cause more air to be behind the ball, thus more force to push it out. Overboring surrounds the ball and more air escapes around it. There are hundreds of arguements saying one is better than the other. From what I am seeing though, it appears that underboring is more “accurate” because it utilizes the air more effeciently, thus eliminating some of the unnecessary “Vortex Shedding” during the initial flight. An example of FPS rising between bore sizes can be seen here:

A video that’s been removed used the following:

The numbers from the video–

He uses three different barrels, so porting and design are different, thus it can’t be used as a “scientific test” but you get the idea. If you want to dig it up, the actual PunkWorks tests show that efficiency and consistency increases with underboring.

Video of what overboring looks like:

As you can see in the overboring video, you have a lot of open space around the ball inside the barrel. Thus, decreasing the effeciency of the air pushing the ball out. This is why Flatlines (a large bore) typically love a larger ball like marbalizers. Once the ball begins to travel away from the gun “Vortex Shedding” comes into play. But, the initial departure of the ball is affected by the effeciency/consistency of the air pushing it out. The problem with underboring is that you have to be exact or else you begin to break paint like crazy. If you underbore by more than .008 you are going to break a lot of paint. They recommend you don’t underbore any more than .003 or else your chances of breaking paint and screwing with effeciency/consistency increase. What does this mean? If your paint is .685 and you want to underbore, don’t go any lower than .682 for the barrel bore size if you want to be “safe”.

Underboring doesn’t increase accuracy, but it helps to maintain it. 

1) Realize paint is getting smaller (.682-.685 on average).
2) If accuracy is a concern, buy better paint.
3) If accuracy is a concern, get an underbored barrel (.682, .684 or .687) but be aware that shells swell in humidity. If they swell too much, they won’t pass through the barrel, or will break inside.