It’s a common misconception that simply installing things like bore-up kits and Type 0 cylinders in your gun will allow you to crank a higher FPS
out of your average AEG. It’s also incorrect to think that you can just throw any length barrel into any AEG and expect it to work perfectly with no negative affects. Which cylinder type you pair with a certain range of barrel lengths is very important in order to optimize both your AEG’s FPS as well as it’s efficiency.
In order to understand why this pairing is important, you should first become acquainted with some basic concepts. While your airsoft gun
is not an actual firearm, it still follows some of the same principles. Real firearms operate by using the expanding gases produced as the gunpowder is ignited to propel the bullet down the barrel. In a similar fashion, your AEG uses the air contained in the cylinder to push the BB down the barrel.
So what’s the problem here? The problem is that with a real firearm, the ignition of the gunpowder produces a large amount of gas with which to propel the bullet. Any excess gas is simply released through the end of the barrel once the bullet leaves the gun, at which point the bullet has reached it’s maximum velocity, and immediately begins to decelerate thereafter.
Don’t worry if you’re still not getting it at this point; more explanation is on the way. Unlike the actual firearm which has a large amount of gas with which to propel the bullet, an airsoft AEG is limited to the amount of air that can be contained within its cylinder. Because only a limited amount of air is available, in order to take full advantage of it the correct cylinder type/barrel length combination must be used.
This is as good a time as any to hit you with some math and physics. The entire concept between pairing your cylinder type with your barrel length appropriately is that you want the volumes to match as closely as possible.
Say you want to use a 500mm barrel in your standard length M4 and cover the excess exposed barrel with a mock suppressor. It is most likely equipped with a Type 3/4 (I will explain this below) cylinder from the factory. The problem you will encounter with this setup is that you are trying to push too little air down a very long barrel. In other words, the volume of your cylinder is significantly lower than the volume of your barrel. This will result in lower FPS because your BB will begin to slow down inside of the barrel once it reaches the point where the volume of air behind the BB matches the volume of air that the cylinder can contain.
In order to optimize your setup, you want the BB to reach its maximum velocity at the end of the barrel, just as it’s exiting. As in the example I just explained, if you have too little air behind the BB, it will begin to slow down before it’s even left the barrel.
Now what about your shorter barreled weapons? Yes, occasionally you will see some gain in FPS, but not always. This is where the opposite example comes in in which you might have an SMG-type weapon, and wish to install a Type 0 cylinder. While you will not see any drop in FPS, expecting gains from the new cylinder may not always be correct. The reason being that although you are pushing more than enough air through the barrel, once the BB leaves the end of it, the rest of that air dissipates and is no longer pushing the BB. It’s essentially just a waste of the extra air.
In basic geometric terms, both the barrel and cylinder are considered cylindrical bodies. The volume of a cylinder is computed by:
V = pi*(r^2)*h
In other words: Volume = Pi * cylinder radius squared * cylinder height (or length)
Following this formula, you can compute how much volume both your cylinder and barrel contain in order to achieve the correct combination. If you are unfamiliar with this concept, don’t fret. I will clearly explain the cylinder and barrel relations so that you don’t have to try to compute these volume values yourself.
I know that up to this point I’ve thrown some terms at you that you might not be familiar with, so we’ll take a little break to take a look at them and more.
Type 0 cylinders
– these cylinders do not contain any ports (holes in the cylinder)
Type 1/2 cylinders
– these cylinders contain ports halfway down the cylinder
Type 3/4 cylinders
– these cylinders contain ports 3/4 of the way down the cylinder, measured from the front (or cylinder head end) of the cylinder
Type 4/5 cylinders
– these cylinders contain ports 4/5 of the way down the cylinder, measured from the front (or cylinder head end) of the cylinder
– these kits contain completely new parts (cylinder, cylinder head, piston head, air nozzle
) which have been designed to allow for a larger volume of air to be stored and pushed down the barrel. These kits are intended for use with very long barrels generally exceeding 600mm.
Here is a list of what ranges of barrel lengths which cylinder types are recommended for:
Type 1/2: 110-170mm
Type 3/4: 270-430mm
Type 4/5: 364-460mm
Type 0: 450-580mm
As stated above, you want to get your volumes of your cylinder and barrel to match up as closely as possible. Having less volume in your cylinder than in your barrel will create FPS problems because the BB will begin to slow down before it even makes it out of the barrel. While a little more volume in your cylinder than in the barrel will not hurt anything, a general rule is it not have more than twice the volume of your cylinder as is in the barrel. This can cause problems due to turbulent air flow following the BB out of the barrel, but that’s a lesson for another day.
With thanks for the article from Richmond airsoft