Vents in Cylinder

[Dead_Fred]

Hi,

Ive just converted a A&K sr25 to an assault rifle size so ive downgraded barrel size from 500mm (or whatever it comes with) to a 363mm (or around there) twist barrel. The fps is holding about 310-330 and the bb's are going straight but my gardens quite short (only able to shoot max of 15m or so) so over large distances the fact i didnt change the cylinder (the sr25 had no vents/holes in it), would it cause problems? I can remember reading somewhere you have to match the cylinder to the barrel size but i didnt read the article.

Cheers
Phil

[kurt458]

Re: Vents in Cylinder

Yeah it is advised but if you have a upgraded piston zany piston head then I would say a vented cylinder would allow a greater airflow

[sj_asc]

Re: Vents in Cylinder

There is no harm in keeping the non ported cylinder, it's just for greater efficiency with your average weight BBs. It will very slightly hinder fps but will carry a greater potential for energy transfer through heavier weight BBs. With your typical .20g youl probably find the muzzle report is a little louder, this is just excess exhaust pressure after the bb has left the barrel that would otherwise be there propelling the bb to near terminal velocity in the previous length barrel.

[skullfacedinfidel]

Re: Vents in Cylinder

a non-vented cylinder in some cases can cause a vacuum where the BB ahead is sucked back by the piston moving backward.. only had this happen on my m16 which has really got airseals and a long tightbore.

[humphriesryan]

Re: Vents in Cylinder

Type 0
Hole: None
Barrel Length: 450-580mm
Examples: Aug, M16, AK47, G3

Type 1
Hole: 4/5
Barrel Length: 364-460mm
Examples: M4, Scar, G36K

Type 2
Hole: 3/4
Barrel Length: 227-330mm
Examples: M4, MP5, P90

Type 3
Hole: 1/2
Barrel Length: 110-170mm
Examples: MP5K



Maybe this helps

[Skolob]

Re: Vents in Cylinder

I reality it makes feck all difference. as mentioned itjust means the pistion starts working a little earlier and excess pressure is wasted. If you have a vented piston head then the suction effect shouldn't really have an effct. I've rin my 249 pata (363 battel) for a long time with a full cylinder.

[Dead_Fred]

Re: Vents in Cylinder

Cheers for the response everyone, sorry for the delay, aint had a computer for the week.

ill leave it as it is then for the time being, don't really want to have to open it up again till i need to.