Need help with Modify Cylinder Upgrade

[RandyAB]

Hello all.....bought a Modify cylinder/piston upgrade. The stainless cylinder has an eliptical hole in it which I assume goes to the rear. Is there a particular orientation for this? (ie: up, down, either side)? Thanks

[StrikeFreedom]

Usually it's on the side, but really it doesn't matter. Just make sure it's near the spring guide side.

[RandyAB]

Thanks Strike....you know what it is there for?

[yuhaoyang]

porting to correct the air volume that gets shot through the barrel.
Matching it to the barrel length

[RandyAB]

How come the stock one doesn't have the hole?

[Amos]

Because it's for a different barrel length, Depending on where the hole in the cylinder is dictates what barrel length it's for.

What gun do you have, and what length inner barrel do you have?

[Sha Do]

For example;
-a center ported cylinder would be for barrel lengths that are short (ie, MP5, P90)
-a 3/4 ported cylinder would be for medium length barrels (ie, MP5 SD6, M4)
-a non ported cylinder would be for long barrels (Ak, AUG, M16)

The reason for the porting is to match your cylinder volume to your barrel volume.
The reason for matching your volume is so you are not forcing more air than is needed down the barrel behind the BB. If you do, it creates a "blow by" effect, which causes an instability in the flight of the BB when it leaves the barrel.....throwing consistent accuracy out the window.

SHA DO

[RandyAB]

The gun is an SRC M4A1. I'm just curious because according to your explanation the stock cylinder should have been 3/4 ported. The inner barrel is 370mm.

[Amos]

370? Are you sure it's not 363 (standard M4 length)



That's the Prometheus version, the modify version will have ports like that, only with a much wider opening.

[venture]

Yup, should have been. When you put it back together put the proper cylinder for your barrel. Performance will be optomized then.

Who will step up and make a pictogram of cylinder picture beside what its supposed to be used in? So we can post that up whenever we get a cylinder porting question.

[RandyAB]

What is the "proper cylinder"? The aftermarket one or the stock one? I got the 370mm spec from the 007 website.

[StrikeFreedom]

370 or 363, how come the stock SRC cylinder is non-ported?

[Jugglez]

Originally Posted by RandyAB

What is the "proper cylinder"? The aftermarket one or the stock one? I got the 370mm spec from the 007 website.

The cylinder that came with your Modify M4A1 cylinder set would be the appropriate cylinder for your barrel.


The lesser gun companies (especially the clone companies) cut all of corners when building their guns, putting the same non-ported cylinders in all their guns is not uncommon.

[THe_Silencer]

I installed an Ak length tightbore in my P90. Would taping the port in my cylinder improve FPS?