Ideal Inner Barrel Length (AEGs)

"Longer are Better ?"
 This topic has been discussed over and over again, but to some newer Airsofters, this misconception still show up often.
So let me talk more in depth about inner barrel length in this post.

When it comes to upgrading a rifle (whether AEG/ Gas sniper/ Spring BASR),
most of time "replacing inner barrel" shown at the top of "to-do" list.
Replacing inner barrel with an aftermarket options supposed to improve Airsoft rifle`s overall performance. But in some cases things just go wrong after installment, FPS drops, shot inconsistency, bad accuracy, weak trajectory, etc.

Aside from faulty/ bad quality replacement barrel, improper installation, misalignment (which not covered in this post), there is also another reason for those performance degradation on upgraded rifles. I will call this "Inner Barrel Mismatch". This means the barrel is not suitable for the rifle without further adjustment.

AEG-DMR has been a really popular platform for all-around sniper rifle these days. So, i want to cover AEG-DMR in my first "Ideal Barrel Length" post.
Let`s say you are building a AEG-DMR with M733 as its base, and first thing u want to do is increasing barrel length, because it was said that longer barrel gives better range, higher fps, and more consistent accurate shots. Now, you need to specifically define HOW LONG  your barrel need to be to achieve mentioned improvement. Assume you have standard inner barrel length of  300mm, replacing stock one for 650mm  tightbore right away, will NOT always give you improved performance over stock one.

Why?

When you shoot, your cylinder would produce certain amount of air pressure to push bb out from the barrel, on stock configuration, amount of air pressure generated by cylinder unit are just enough to push bb out from it`s designated inner barrel length.

So, theoretically a stock M16 AEG (509mm barrel) will have more cylinder volume compared to a stock M733 AEG (300mm). Longer Barrel replacement on shorter rifle cause Cylinder losing its air-pressure before bb leave inner barrel, resulting weak trajectory, reduced range, and often FPS drop. Otherwise, shortening inner barrel on longer rifle without adjustment and fine tuning will result in excessive pressure even after bb leaving the barrel, which cause inconsistency, and might damage internals in long term due higher impact from piston. Longer inner barrel needs more air-pressure from cylinder, shorter one need less air-pressure.

Conclusion

If you want to stick with longer barrel that you have already purchased, you might also want to swap your Cylinder as well.
Usually shorter rifle have a "slot" on the side of it`s cylinder. This slot reduces effective compression room of cylinder, making it suitable for shorter inner barrel.
Replacing cylinder to full (non-slotted) type will ensure you have maximum volume required for longer inner barrel, or you can even use BORE-UP cylinder for more volume.
 There are soooo many choice of aftermarket AEG cylinder, the choice is yours, just remember long barrel = full/bore up cylinder.
I have had a Snow Wolf M82a1 (seen on my greeting post). The first thing i done back then, was installing bore-up cylinder over stock one, and it performed like magic considering enormous stock barrel length of 650mm paired with tiny cylinder of V2 gearbox.

Hey, what about Gas sniper or Spring BASR?? there aren`t many choice of bore up cylinder for Spring BASR, even Gas sniper don`t even have any cylinder, what should i do then?

UPDATE:
Spring BASR here !

Stay tuned, i will be back with another post on these :D !