Barrel Length to Cylinder Size

[Pewpewpetie]

Hi currently working on my specna arms ak and read somewhere about cylinder volume has to be the right size for installed barrel or you will loose fps. My question is this v3 gearbox has a standard non ported cylinder which came with a 455mm barrel (stock), all v2 gearboxes I've worked on have had the same cylinder but come with 363mm barrels. I'm upgrading the hop to a lonex with prommy purple just unsure on barrel length.

 

[Adolf Hamster]

unported sounds right for a full length ak.

if you're switching barrels then just keep as close to the stock length as you can.

aeg's tend to be pretty forgiving on the whole voluming thing, it's really stuff like hpa's where volume matching becomes a real issue (although granted on hpa's you can also dial it in to perfection with relative ease)

 

[Shaydee]

Easiest to stick to around the stock length. As Hamster says unported is pretty much the standard in full length AKs, hell I'm pretty sure the cylinder in my 74u and 105 are full and I don't see any issues with them on shorter barrels.

Also, purely my $0.02 here - if you haven't got any air seal issues or the hop unit itself isn't broken or plain garbage, I feel like it's a bit of a false economy changing it out.

 

[PopRocket123]

My dad did some experiments a few years ago. He found that for a cylinder ported to work with a piston with two teeth removed, the optimum barrel length for joules and consistency was around 310mm. This was only marginal differences though so don't worry unless you're really min-maxing your build.