Manufacturers matching the wrong cylinder type to barrel length.

[Asomodai]

Hello all. 

Quick question. 

My new SRC XM8 had a standard 363mm Aluminium barrel, but paired with a Full Cylinder. This I would assume means that it over volumes. There is a belief that this potentially introduces some inaccuracy, but does it affect FPS?

I replaced the old barrel with a ZCI 6.02 363mm barrel. It increased my FPS by around 20, which means I am now over 350FPS. Would installing one of my spare 4/5ths type cylinders decrease or increase the FPS? Or would it make no difference? I can always change the spring, but would rather save a bit of money if I could. 

Lastly. Why would a manufacturer put in a full cylinder for barrels that don't require it? To reduce the amount of different gearbox lines to keep costs down?

Cheers!

 

[E21A]

4/5ths cylinder will reduce FPS. Less volume = less air compressed = lower FPS 

 

[Asomodai]

4/5ths cylinder will reduce FPS. Less volume = less air compressed = lower FPS 

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I see a lot of conflicting information online about what inner barrel length would be suitable for a 4/5th cylinder. Is 363mm appropriate?

 

[E21A]

Calculate the volumes, there’s plenty of tools online that’ll do it for. Just input a few basic measurements. As to what ratio you want, I can’t really help. I know it’s about 2:1 for snipers/DMR but not sure if it’s the same for AEGs 

 

[PopRocket123]

After adjusting AOE I think the optimum length for an AEG barrel running .28s is about 310mm with a tightbore

 

[Asomodai]

Calculate the volumes, there’s plenty of tools online that’ll do it for. Just input a few basic measurements. As to what ratio you want, I can’t really help. I know it’s about 2:1 for snipers/DMR but not sure if it’s the same for AEGs 

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I cant seem to find the optimum ratio. Mine comes out at around 3:5 with the correct Cylinder dimensions and barrel dimensions. I am unsure as to what this means

 

[E21A]

Is that with the full cylinder or the 4/5ths? 

 

[Asomodai]

Is that with the full cylinder or the 4/5ths? 

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Full cylinder. 

With a 4/5ths I am unsure where to measure to. Where the hole begins or where it ends (From the Cylinder head side.)

 

[E21A]

From the cylinder head to where the hole starts. You be compressing any air until the piston head passes the hole. 

 

[Asomodai]

From the cylinder head to where the hole starts. You be compressing any air until the piston head passes the hole. 

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I got this ratio. 

2.28 : 1

 

[E21A]

Seems very high that! I’d personally aim for about 1.8:1 to start with, should be more than adequate. What weight BB will you using? 

 

[Asomodai]

Seems very high that! I’d personally aim for about 1.8:1 to start with, should be more than adequate. What weight BB will you using? 

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Hoping to use .28's or .30's if the hop unit can manage it. 

Either way the 4/5ths Cylinder will probably be better then the full cylinder if my calculations are even remotely correct right?

 

[E21A]

Yea, it’ll be better than full. Try it and see, if it’s no good you can always extend the hole to reduce the ratio 

 

[Adolf Hamster]

Cant say i've ever noticed a significant difference in fps when changing volume type. Certainly not compared to actual short stroking the piston.

Also cant see i've seen much difference in accuracy either, at least not compared to most other tweaks.

 

[Samurai]

Overvoluming in a v3 AEG is not much of a problem.

It is much louder because the bb leaves the barrel before the piston impacts, so it's not blocking the sound of it.

The v3 gearbox can handle the increased impact force of the piston. Normally the air behind the BB acts as a cushion to soften the impact. The weaker v2 boxes can break because of this.

With heavy BBs you will have some joule creep. Make sure you are below the site limits with your BBs if the site chronos on the BBs used.

You might have more fps with 3/4 cylinder because the BB might leave before the piston reaches full speed. This depends on many factors.

 

[Adolf Hamster]

never really noticed joule creep worth mentioning on aeg's, you'd need a pretty heavy piston which is counter to most players desire to keep the rate of fire at something decent.

it's more of an issue with gas guns because the pressure is constant.