How do different barrel lengths affect accuracy?

[intrepidaf]

I'm new to airguns and looking to understand more about how different barrel lengths affect accuracy. Can anyone explain the relationship between barrel length and shot consistency?"

I found some info on this forum and google regarding the subject but was unsure of which were true.

1. Longer barrels always result in better accuracy: While barrel length can influence accuracy, it's not the only factor. Factors like barrel quality, ammunition used, and the shooter's skill also play significant roles.
2. Shorter barrels are always less accurate: While longer barrels can provide more stability to the projectile, shorter barrels can be just as accurate if they are well-made and properly calibrated.
3. Barrel length directly correlates with projectile velocity: While longer barrels can potentially increase projectile velocity due to more time for the gas to act on the projectile, other factors like air pressure, barrel quality, and projectile weight also play roles in determining velocity.
4. Barrel length is the most important factor in accuracy: While barrel length is important, factors like barrel quality, bore consistency, and the quality of the ammunition are equally important in determining accuracy.
5. Shorter barrels are always louder: While it's true that longer barrels can sometimes help dampen the sound of the shot, factors like the type of airgun and the air pressure used also influence noise levels.

 

[Sawney Bean]

Longer barrels tend to help with efficiency, velocity and noise so they're more desirable on airguns than on firearms. They don't really increase accuracy, but they can make the gun hold more steady. The minimum barrel length for a bb gun to "stabilize" a bb is something like 4 inches. For a pellet I doubt there is a minimum length since pellets are somewhat self stabilizing.

 

[phoenix_cow]

I'm new to air gunning my self but I know a bit about how barrel length effects regular guns. I can only assume that it is more or less the same.
As soon as a pellet leaves the barrel it is no longer propelled by air and it is effected by gravity.

What this means is:
To get the same amount of velocity from a shorter barrel as a longer barrel you need a faster blast of air (larger transfer port), you want all the stored energy you have to be used up right as the pellet leaves the barrel (well maybe a bit after it leaves), more often you won't be able to get the same speeds no matter what you do.
As soon as the pellet leaves the barrel you are no longer "pushing" it. That is why longer barrels have better velocity; they have more time to use that potential energy.

Even if you get the same velocity your pellet they will be effected by gravity and other forces sooner, because it leaves the gun sooner then a long barrel. This means having to aim higher and taking in account wind more. With firearms it isn't to big a deal, unless firing from a huge distance. But pellet BC and velocity isn't that good compared to bullets, so the effect can be quite large. A few inch difference means a few less/more inches you have to account for.

Again, I'm a beginner to air guns so take what I say with a grain of salt.

I hope this helps.

 

[delooper]

Largely a repetition of Sawney but:

1) No.
2) No.
3) Yes, if the other variables remain the same (air pressure, plenum capacity, etc)
4) No.
5) Yes, if the other variables remain the same.

The loudness of a gun largely has to do with the back-pressure (and volume) behind the pellet when it leaves the barrel. So if your barrel is shorter and you fire with the same amount of air, there'll be more back-pressure when the pellet leaves the barrel. That results in a more powerful shockwave, i.e. more noise.

 

[subscriber]

Longer barrels are more flexible at a given outer diameter. That means the muzzle "waves about" more while the pellet is travelling down the barrel, from the shock of the air pressure being applied. This often makes longer barrels shoot larger groups, or makes them more "pellet fussy". Meaning, they may shoot acceptably with a smaller variety of pellets.

 

[Spartan]

Largely a repetition of Sawney but:

1) No.
2) No.
3) Yes, if the other variables remain the same (air pressure, plenum capacity, etc)
4) No.
5) Yes, if the other variables remain the same.

The loudness of a gun largely has to do with the back-pressure (and volume) behind the pellet when it leaves the barrel. So if your barrel is shorter and you fire with the same amount of air, there'll be more back-pressure when the pellet leaves the barrel. That results in a more powerful shockwave, i.e. more noise.

I think this is a great summary. It is a long-standing myth that longer barrels lead to greater accuracy. Both for airguns or PBs. Don’t know for sure, but it may stem from PB guns that are designed for very long range shooting having longer barrels in order to take advantage of higher speeds. So perhaps people started to assume this pattern of long barrels for long range shooting also equaled more accuracy. Just guess.

 

[subscriber]

Or, a longer barrel provides a longer sight radius with open sight, for more precise sighting, leading to better performance on target.

 

[Scotay42]

Or, a longer barrel provides a longer sight radius with open sight, for more precise sighting, leading to better performance on target.

Only with open sights. A scope makes it the same no matter the length of the barrel. Length only helps in speed/power for barrels and stability when talking lower support, ie bags, bipod, rest etc. Longer bipod support will increase stability making it easier to hold on target (long gun vs bullpup).

 

[Stubbers]

If my barrel is long enough to extend up to 1" away from my target, I will hardly if ever miss.

Jokes aside, barrel length can provide a smoother, softer ride with less high pressure air deviating a pellets trajectory upon exit. If there is enough high pressure air as the pellet exits the muzzle, it will try to out pace the projectile and not uniformly. Try to win a 100 yard bench rest with a 9" barrel, I implore you. The GK1 can make the power, but lets see it take home a crown to put the barrel length accuracy 'myth' to rest...

-Matt

 

[uglymike]

Or, a longer barrel provides a longer sight radius with open sight, for more precise sighting, leading to better performance on target.

agree

 

[Star7]

A PCP rifle used for Olympic shooting has a short barrel with a long "bloop tube" so as to give the maximum sight radius allowed. The short barrel allows the pellet to clear in a short period of time with just the necessary velocity to stabilize in the 10m distance to target.

A spring piston system gives another level of complexity in that piston travel, air cushion bounce and all of that will affect recoil in the period the pellet is still in the barrel.

For hunting, max velocity in a spring piston rifle will be achieved, usually in less than 12" but a PCP will depend on the power plant and how much air it dumps. Long sight radius, of course is only useful for open sights but the balance of the gun and moment about center of mass needs consideration.

There's a bunch of considerations that will change your design based on end use.

 

[LDP]

The longer barrel equates to better accuracy comes from the old days when people used open sights. The longer sight radius makes it easier to consistently line up the sights. When you are using a scope it doesnt matter.

 

[bucketboy]

Neither Barrel length or it’s straightness affect accuracy, however if all things are equal, barrel length does affect power, on average 15fps faster per inch. It is possible to get good power from a shorter barrel but shot count will suffer and noise will increase

Bb

 

[delooper]

The longer barrel equates to better accuracy comes from the old days when people used open sights. The longer sight radius makes it easier to consistently line up the sights. When you are using a scope it doesnt matter.

But on the extreme non-straight end, as bucketboy's example illustrates, the fouling a helical barrel would endure must be impressive.

 

[bigHUN]

Longer barrels vs shorter barrels can be more accurate - but indirectly.
Speaking now for all scenarios you shooting same pellet weights with same speed at same distance - from each barrel.
300 mm - 400 - 500 - 600 - 700 - 800 mm long barrels
Longer barrels are less finicky with tunes and you can easier finetune the Reg and Dwell until the pellet is still running inside rifling and possibly shave off most of the blow by at muzzle.
You can actually feel that on the bark. I am not talking here 10 meters rings (those are specialty guns a totaly different ballgame) but take the game @ 50 or eventually 100.

 

[Caliber 22]

Some people say that with longer barrels the shooter can cause movement after the valve opened and while the pellet is traveling in the barrel and cause it to fly in a different direction.

 

[delooper]

Some people say that with longer barrels the shooter can cause movement after the valve opened and while the pellet is traveling in the barrel and cause it to fly in a different direction.

In a springer you get far greater affect than that, and people get consistent aim with appropriate technique.

 

[Caliber 22]

In a springer you get far greater affect than that, and people get consistent aim with appropriate technique.

Jip. In a springer it is a mechanical impact that is way faster and more violent than the human movement that can be imposed on a pcp.

 

[JDGriz]

Larger weight could dampen movement more and increase steadiness when shooting offhand, to a point. But otherwise shorter barrels are stiffer and more accurate.
In PBs, longer barrels are also used to lower chamber pressures, with slow burning propellant which takes some length of barrel to combust.

 

[Caliber 22]

But otherwise shorter barrels are stiffer and more accurate.

Lot's of people say so and that is a half truth. That is why it is important to tune your pcp to a certain pellet or slug to get the barrel harmonics in tune. It is not that the pellet flies better at a specific speed as it does fly good at different speeds from different rifles.
The same is true for PB reloading. The bullet does not have a preferred speed, it is about barrel harmonics to let the bullet exit the barrel at the same position in the harmonic curve.
Shorter of longer barrel does not matter, you tune according to each barrel.