Pseudotectonic
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- May 7, 2022
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Does barrel length affect accuracy? Yes? No?
How? And how much?
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Let's do a simple thought experiment. Using maths, and a very typical situation. I have a variable barrel that goes from 50 mm to 550 mm. And I have an imaginary target at 30 metres. I want to find out the different ways the difference in barrel length can affect the grouping diameter.
For the purpose of this calculation, we can eliminate the factors of air volume and hop up. Because for every build these would have been tuned accordingly to work with each barrel length. They will all have been tuned to output the same joule with the same BB and with the same hop up performance.
Therefore this calculation deals only with the geometrical effects of a longer or shorter barrel.
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Diagram A: Spread introduced by barrel BB travel
Assume the barrel is a stock 6.05 mm barrel. The BB has a typical 5.95 mm diameter. Therefore the variation is 0.1 mm.
Assuming the BB travels in more or less a straight line, this 0.1 mm variation at the barrel exit will give us the worst case BB trajectory.
The final spread diameter at 30 metres is therefore a simple triangle calculation.
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Diagram B: Spread introduced by inner barrel wobble inside outer barrel
Due to the construction of airsoft, the inner barrel is normally not fixed inside the outer barrel, but simply rests inside with a little clearance space around. During the firing cycle the gun will definitely be subject to vibrations of all sorts, making the inner barrel essentially wobble inside the space it occupies.
Assuming this clearance is 0.4 mm (measured from an AEG) we can similarly calculate the spread it creates at 30 metres.
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Diagram C: Spread introduced by difference in ergonomics
A longer barrel will allow you to hold it steady at two further apart locations, because of the longer handguard. This can be fully exploited to create a more stable barrel.
Assuming your most steady hand will involuntarily sway within a 2 mm range, we can again extrapolate its effects on the grouping using the same calculation.
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Factor D: Wind
There is no diagram for this because wind is not affected by barrel length. We assume a moderate wind affecting our BB at 30 metres to introduce a spread of 50 mm.
--
Results:
In the order of significance, the barrel length can influence the accuracy through:
I will discuss each below.
The biggest advantage of a longer barrel has surprisingly nothing to do with the actual ballistics of the BB, but the effect of simply having a longer stick to hold onto gives you a better control of the aim. For shorter barrels below 200 mm, the ergonomic disadvantages will affect your accuracy a lot for long range engagements, although the shorter builds are better for CQB where accuracy is less important than manoeuvrability. The biggest thing you can do to exploit the advantages of a longer barrel in terms of accuracy will be to eliminate hand sway as much as possible while making use of the longer form factor. That means using bipods or resting your gun at something solid as much as possible, and so on. Again it remains true that it is 99% the user and 1% the gun.
Even with worst case geometrics, the inner barrel wobble and BB travel inside barrel does not really introduce much spread once you go above 200 mm barrel length, where it generally becomes less of a problem than actual wind blowing your BB. Above say 300 mm, the effect will become so small it becomes virtually no difference in most practical situations.
--
Recommendations:
Conclusions:
Nothing is new here, but I guess you can't really snipe with an MP5K. But you can potentially snipe with an MP5.
How? And how much?
--
Let's do a simple thought experiment. Using maths, and a very typical situation. I have a variable barrel that goes from 50 mm to 550 mm. And I have an imaginary target at 30 metres. I want to find out the different ways the difference in barrel length can affect the grouping diameter.
For the purpose of this calculation, we can eliminate the factors of air volume and hop up. Because for every build these would have been tuned accordingly to work with each barrel length. They will all have been tuned to output the same joule with the same BB and with the same hop up performance.
Therefore this calculation deals only with the geometrical effects of a longer or shorter barrel.
--
Diagram A: Spread introduced by barrel BB travel
Assume the barrel is a stock 6.05 mm barrel. The BB has a typical 5.95 mm diameter. Therefore the variation is 0.1 mm.
Assuming the BB travels in more or less a straight line, this 0.1 mm variation at the barrel exit will give us the worst case BB trajectory.
The final spread diameter at 30 metres is therefore a simple triangle calculation.
--
Diagram B: Spread introduced by inner barrel wobble inside outer barrel
Due to the construction of airsoft, the inner barrel is normally not fixed inside the outer barrel, but simply rests inside with a little clearance space around. During the firing cycle the gun will definitely be subject to vibrations of all sorts, making the inner barrel essentially wobble inside the space it occupies.
Assuming this clearance is 0.4 mm (measured from an AEG) we can similarly calculate the spread it creates at 30 metres.
--
Diagram C: Spread introduced by difference in ergonomics
A longer barrel will allow you to hold it steady at two further apart locations, because of the longer handguard. This can be fully exploited to create a more stable barrel.
Assuming your most steady hand will involuntarily sway within a 2 mm range, we can again extrapolate its effects on the grouping using the same calculation.
--
Factor D: Wind
There is no diagram for this because wind is not affected by barrel length. We assume a moderate wind affecting our BB at 30 metres to introduce a spread of 50 mm.
--
Results:
In the order of significance, the barrel length can influence the accuracy through:
- - Ergonomics
- - Inner barrel wobble
- - BB travel inside barrel
I will discuss each below.
The biggest advantage of a longer barrel has surprisingly nothing to do with the actual ballistics of the BB, but the effect of simply having a longer stick to hold onto gives you a better control of the aim. For shorter barrels below 200 mm, the ergonomic disadvantages will affect your accuracy a lot for long range engagements, although the shorter builds are better for CQB where accuracy is less important than manoeuvrability. The biggest thing you can do to exploit the advantages of a longer barrel in terms of accuracy will be to eliminate hand sway as much as possible while making use of the longer form factor. That means using bipods or resting your gun at something solid as much as possible, and so on. Again it remains true that it is 99% the user and 1% the gun.
Even with worst case geometrics, the inner barrel wobble and BB travel inside barrel does not really introduce much spread once you go above 200 mm barrel length, where it generally becomes less of a problem than actual wind blowing your BB. Above say 300 mm, the effect will become so small it becomes virtually no difference in most practical situations.
--
Recommendations:
- - Below 200 mm is strictly for CQB. The BB, the barrel, and the gun itself will all suffer from stability issues for making accurate shots.
- - While barrel length affects accuracy in pure mathematics, the ballistic effects will have become virtually irrelevant above 300 mm.
- - Longer barrels (longer guns / sniper rifles) can potentially have better groupings, with the right skills, and probably with the right bipod.
- - The best method to improve accuracy is improving largely your skills, not your gun.
Conclusions:
Nothing is new here, but I guess you can't really snipe with an MP5K. But you can potentially snipe with an MP5.
