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It's widely known that changing inner barrel length and changing inner barrel diameter change the airsoft BB velocity. Physics tells us that. But exactly how much does it change by? It's anybody's guess. All sorts of numbers are posted on Internet forums and discussions. Some people claim it's negligible. Some people claim it's significant. What is it really?
In this article, we will explore this topic with real quantifiable results. We will use scientific method of observation and analysis to determine exactly how much these changes make. We will provide full disclosure to how the test is conducted and what equipment are used. Does changing inner barrel makes that much difference? Let's find out.
| 1: | 279 FPS |
| 2: | 278 FPS |
| 3: | 273 FPS |
| Average: | 276.7 FPS |
| 1: | 327 FPS |
| 2: | 324 FPS |
| 3: | 321 FPS |
| Average: | 324 FPS |
| 1: | 354 FPS |
| 2: | 353 FPS |
| 3: | 349 FPS |
| Average: | 352 FPS |
Fact 1: When the inner barrel diameter is the same (6.04mm), changing the length by 100mm causes the velocity to change by 28 FPS.
Fact 2: Changing the diameter by 0.03mm and the length by 65mm causes the velocity to change by 47.3 FPS.
Fact 3: Changing the diameter by 0.03mm and the length by 165mm causes the velocity to change by 75.3 FPS.
Let's start by extrapolating the velocity difference of a 6.04mm diameter 110mm length inner barrel using one relationship:
xFPS 65mm
----- = -----
28FPS 100mm
xFPS 65mm (28FPS)
= -----
100mm
xFPS = 18.2FPS
The result above shows that out of the 47.3 FPS difference, 18.2 FPS is from the change in length. In this extrapolation, the 0.03mm difference results in 29.1 FPS change.
Then let's extrapolate the velocity difference of a 6.04mm diameter 110mm length inner barrel using the other relationship:
xFPS 65mm
----- = -----
28FPS 100mm
xFPS 165mm (28FPS)
= -----
100mm
xFPS = 46.2FPS
The result above shows that out of the 75.3 FPS difference, 46.2 FPS is from the change in length. In this extrapolation, the 0.03mm difference results in 29.1 FPS change.
Wow. In both extrapolation, the 0.03mm inner barrel diameter difference causes the exact same velocity change. It's either the diameter and length changes produce absolute linear results or I did something wrong in this analysis. If the former is the case, then we can accurately determine potential velocity (the velocity of the inner barrel you want to buy) based purely on one observational data (the velocity of the inner barrel you already have).
I can get more results and perform more in-depth analysis if I have more inner barrels. If anyone want to donate some inner barrels, please let me know.
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