A question that is often on many beginning airsofter’s minds is whether or not the length of their barrel has any real effect on the accuracy of their shooting.
This question is not only a frequently asked one, usually pondered as one gazes longingly at a high performance upgrade, but can also be something of a hot button issue in both airsoft and the real steel world.
In this article we’ll discuss the effects, if any, that a longer or shorter inner barrel can have on your airsoft gun, and hopefully lay to rest some common misconceptions that many otherwise rational individuals fall prey to.
Inner Barrels and FPS
Generally speaking, and with gas and spring powered airsoft guns in particular, a longer inner barrel does have some effect on velocity (as measured in FPS).
All things being equal, the longer the barrel the more time the gas will have to expand and carry the BB out of the barrel and towards the target.
A significant (couple inches at least) increase in the length of the barrel should, in theory at least, cause a slight increase in FPS.
That said, when dealing with barrel length it’s important to keep compression in mind.
If an airsoft gun’s cylinder cannot properly fill a given barrel’s volume (which tends to increase the longer it is) it can create negative pressure behind the BB that can actually reduce FPS.
Maintaining proper volume balance is actually quite important on a build, whether spring, gas or AEG, and more often than not a significant change in barrel length can necessitate modifications to the internals of the gun as well.
Barrel Length and Accuracy in Airsoft
While barrel length does have a moderate effect on FPS, all things being equal, it (and velocity, too, for that matter) has very little to do with an airsoft gun’s accuracy in the real world.
After all, we’ve all seen long barreled, super cheap, high FPS airsoft rifles that can’t hit the side of a barn beyond 40 feet.
While it is perhaps true that the extremes of barrel length can have an effect on the flight path of a BB, such as by having a super long barrel that exceeds its compression ability or a gun with no barrel at all that can’t stabilize a BB, by and large the length of an inner barrel has almost nothing to do with a gun’s consistency and accuracy.
What does have an effect on accuracy when it comes to inner barrels is the quality of its machining and finish and the hop up unit it is attached to.
Barrel materials, machining and finish
For the most part, a good deal of an airsoft gun’s accuracy comes from the smoothness and straightness of an inner barrel, as well as (to an extent) what it is made of.
Regardless of length, a BB traveling down an inner barrel at speed should ride smoothly on a cushion of air or gas and shouldn’t clip or bump into any obstructions, debris or defects in the barrel that can cause it to lose control, and a good, smooth and straight barrel can go a long way in doing so.
Similarly, the materials from which an inner barrel is made can go a long way in making sure things stay accurate.
Certain materials (high quality stainless steel and brass, for example) can stand up a lot better to the use and abuse of regular airsofting, sending out BB after BB without developing accuracy-killing chips, scratches or dings.
But perhaps more important than the material used is the machining process.
Good barrels tend to come from manufacturers with good quality control and who make sure that, regardless of whether a barrel is made of aluminum, steel or brass, they are sold free of inner defects.
After all, there is no point in buying an inner barrel made from top quality materials if its inside has a more than passing resemblance to the surface of the moon.
Probably more than anything, however, when it comes to accuracy hop is king.
As we’ve discussed in greater detail in our piece on hop ups, hop up units create the spin that allow airsoft’s very round and rather high-drag/non-aerodynamic 6mm BBs to travel further and more consistently towards a target due to the Magnus effect.
A better hop unit that uses a properly shaped bucking and that uses a good quality rubber nub will deliver superior spin that will keep a BB traveling on course for longer periods of time, translating to greater range and accuracy, even if the barrel it is attached to is relatively short (again, all things being equal).
When it comes to airsoft, therefore, a short barreled airsoft gun with a good quality, adjustable hop up will outperform just about any longer barreled airsoft gun that is fitted with a cheap or badly made unit.
In fact, we’d go so far as to say that rather than spending time worrying about the length of their inner barrel, users concerned with improving their accuracy would do best spending time figuring out how to modify or improve their hop up unit.
BB Quality and Weight
Something that many airsofters discount when it comes to accuracy is the quality and weight of the little plastic balls they are firing.
A defect free, smooth surface can go a long way in making sure that a BB travels along a smooth flight path towards it destination by not creating its own turbulence, catching/damaging/jamming the barrel or even breaking apart when fired.
This is why it is always important to look for decent quality BB brands, as they tend to invest a little more in quality control.
Similarly, heavier BBs can help provide greater accuracy.
As a rule of thumb, the heavier the BB, the greater the retention of energy it has and the greater resistance to disturbances in flight, all of which can result in more consistent shot placement.
Overall, the fact that there are many more factors beyond inner barrel length that affect accuracy beyond inner barrel length is the prime reason why many well-made airsoft pistols, such as the relatively low FPS Tokyo Marui MK23 can actually consistently outshoot more cheaply made, powerhouse airsoft rifles.
It can also go a long way in explaining why plenty of sniper builds end up being short barreled.
What About Bore Diameter?
A common misconception in airsoft is that the tighter (or wider) the bore, the more accurate the shooting.
The thinking goes that wider bores will allow a BB to travel on a greater cushion of air, which keeps it centered and stable.
In contrast, others firmly believe that a tighter bore will concentrate the air pressure behind the BB and will have less room for it to “bounce around,” leading it to launch more stably and precisely towards its target.
The reality is that while it’s true that a tighter bore than standard (6.08mm) can squeeze out a little more FPS from a build, the evidence concerning accuracy and consistency either way is mixed at best and there are quite simply too many variables (which can differ between barrels, builds and environmental conditions) when it comes to accuracy to have a simple answer either way.
At the end of the day, while it probably won’t hurt to add a tightbore for some extra power, those interested in improving accuracy would be best advised to focus on improving their barrel quality and hop up.
So When Does Barrel Length Matter
As we mentioned the length of an inner barrel can matter as it relates to compression, needing to fit the volume of gas that the gun can produce.
If a barrel is too short, a BB will leave the barrel before enough pressure has built up, causing inconsistent FPS.
If a barrel is too long for the internals, it can cause negative pressure and reduce FPS.
Some people, CQB players in particular, like to keep things as compact as possible in order to make it easier to maneuver around tight spaces with their airsoft gun, or to help conceal themselves without a big barrel jutting out.
Some of these users will even go so far as to replace the inner barrel with a shorter version (or simply cut and crown it) and shorten the outer barrel to modify their replica in order to get the maneuverability they desire.
Taste and Preference
In a similar vein, most airsoft outer barrels aren’t too much longer than their inner ones.
While some users like the short and compact look of an SMG, pistol or carbine, others may prefer a gun with a nice, big intimidating barrel that can make their opponents experience a moment of existential dread.
Barrel length is one of those topics in airsoft that people love to argue about on forums and that manufacturers love to use as a marketing and sales point.
While it can have some effect on a gun’s FPS and does somewhat factor into considerations of volume matching, taste and maneuverability, inner barrel length has far less of an effect on accuracy and consistency than most people would have you believe.
Those interested in making their airsoft guns as laser-like as possible are far better served focusing on the quality of the barrels and their hop up units than worrying about millimeters of difference.
Will Martin – Will has been into airsoft and paintball for well over 10 years, and has done it all – from upgrading and fixing gearboxes as a tech to building custom airsoft loadouts for his friends to supporting off those friends as a DM.