Stock inner barrel is 560mm, should I go shorter?

[Lollingsgrad]

I've got a King Arms SVD AEG, I'd like to upgrade the inner barrel but the stock one is ridiculously long. I'm planning on shooting 0.4s so I'm thinking about 350-400mm to pair with its approx v2.5 sized cylinder.

I've read that outer barrel length doesn't matter but some people attach the caveat that it can matter if outer barrel doesn't provide enough space for the air to escape into. This is certainly the case with the SVD as the outer barrel hugs the inner right to the end. Does anyone have experience with this being a problem?

 

[IntelligentCelestialBeing]

I dont full understand your question but i hope this answer helps anyway haha 

Its important that you get good balanced compression for the size of barrel you are using and this is done by putting ports (holes) in the back end of the cylinder.

if you have a short barrel weapon and you have a cylinder with no holes in it, the bb will leave the barrel before the air is full compressed resulting in lower than expected fps. So to creatw good balances air compression 1 or 2 holes will be in the cylinder (towards the back). 

For long barrelled weapons like M16s and DMRs  the cylinder will have no holes in them this is because the barrel is longer so youll need more compressed air to push the bb out the barrel and good enough velocity. Having holes in the cylinder with a long barrel will mean less compressed air and more distance for the bb to be pushed out thw barrel, resulting in a decrease of fps. 

So in conculsion its perfectling fine to have a longer barrel and a longer barrel will mean increased range but youll need good balance compression relative to the barrel size. Also just make sure the barrel you decide to purchase fits perfectling in the outer barrel. Also im pretty sure it doenst matter that your outer barrel hugs your inner barrel right to the end. Not really sure what you meant but this but im pretty sure it doesnt matter. And i also didnt understand what you meant by “the outer barrel providing enough space for air to escape into”? Im pretty sure the outer barrels only purpose is to hold the inner barrel so as long as your inner barrel fits perfectly in your outer barrel it doesnt matter. Dont quote me on that tho haha 

Hopefully this has helped i didnt fully understand your question. 

 

[Asomodai]

I've got a King Arms SVD AEG, I'd like to upgrade the inner barrel but the stock one is ridiculously long. I'm planning on shooting 0.4s so I'm thinking about 350-400mm to pair with its approx v2.5 sized cylinder.

I've read that outer barrel length doesn't matter but some people attach the caveat that it can matter if outer barrel doesn't provide enough space for the air to escape into. This is certainly the case with the SVD as the outer barrel hugs the inner right to the end. Does anyone have experience with this being a problem?

There is are issues with the outer barrel as you described. A full and/or bore up cylinder is good to use up to about 509mm if you haven't short stroked the gearbox. If you have short stroked then you need to go under 400mm to make up for the volume shortfall. 

Personally, I have an SVU bullpup and it usually comes with the 670mm barrel, but I am getting a 509mm installed.