AEG Volume ratio question

[Sev]

Hi

 

Whilst contemplating the barrel group options for a build in progress, I came upon a question I can't work out the answer to.

 

In this build I have a cylinder with 23.8mm internal diameter and the piston stroke is 46mm. With the current 6.05mm 280 mm barrel that gives me a ratio of 2.54:1 which is close enough to the limit of 2.5:1. Luckily this build is for CQB and typical field play combined, so that'll work nicely, I think.

 

My question comes with longer-barrelled builds. I've read that longer barrels favour a higher ratio (between 2 and 3.5) because the detrimental effects of a low ratio are exaggerated. The thing is, by my calculations, with a 6.03mm 370mm barrel you would need a stroke of 61mm to hit 2.5. If you tried that in a fast, torque-based DMR build, which is likely short-stroked, how do you gain that extra cylinder volume needed?

 

Either my maths is wrong, my information is wrong or people using longer barrels are running seriously sub-optimal with high-tuned setups. Which is it?

[Immortal]

Say whaaaaaat?! I wish I understood this ratio stuff. I need to learn this!

[Adolf Hamster]

The short version is you don't short stroke a long barrel build.

[Sev]

8 hours ago, Adolf Hamster said:

The short version is you don't short stroke a long barrel build.

 

Ok, makes sense on reflection. How would you avoid PME without shortstroking?

 

The reason I'm keen to understand is that I am planning a DMR build for my next project :D

[Adolf Hamster]

26 minutes ago, Sev said:

 

Ok, makes sense on reflection. How would you avoid PME without shortstroking?

 

The reason I'm keen to understand is that I am planning a DMR build for my next project

 

if you're running a higher fps then you'll get away with it naturally, otherwise you just accept the trade off in speed, if it's a proper dmr you're not really gonna be using full auto anyway.