Hey Najon, is it a ported cylinder?

Yes looks like this minus all the shin and grooves

http://www.airsoftparts.ca/store2/im...4-cylinder.jpg

I'm in class right now so I wasn't able to watch this with sound...

YouTube- CA25 Cylinder Compression Test Tutorial

This seems to be a tutorial on how to check compression.

Thanks Amos! Trying now

Noticed my nozzle doesnt have an o-ring on it, haha time to check the mail box for the parts

I think by the end of this all, I will start upgrading P90's as a side job. I have ran into almost every known problem that could ever exist when upgrading from reverse cylinders, to air leaks to putting the hop up rubber in wrong to even placing the spring in the wrong way.

I was gonna suggest to make sure the cylinder is in the right way :p but it seems like you got it :D

Sounds like you should be sending this thing to a gundoc lol

NO Need Gentlemen and any ladies out there...

I won't say that it is a full success until I chrono my gun however, I just did the compression test with my OLD nozzle and it failed hard, there was no O-ring in the nozzle so I threw that acrossthe room and put in my new one. Passed with flying colours, so I put everything back together.

When I connected to battery up it made the regular sound of my gearbox, only louder. So Everything is working mechanical wise, air pressure being created seems to be creating more force then it was before. I was surprised that the V2 spring guide fit in it but it did and it seems to be doing fine after running the gearbox for a bit.

Aslong as the FPS on my gun is over 320 then I'm happy, just need a chrono now...ugh and flag raiders is so far away, and I hate getting swarmed by all the kid campers there during the day haha

depending on brand, most stock nozzles dont have the oring in it.

You have a 430mm inner barrel and your only getting 290 FPS? you could try to put an extra rubber band in your piston head, it would help expand those o-rings more and get more compression.

Save the gas and do a poor man's chrono instead, at least it can give you a ballpark figure of your fps.

The piston head needs that extra room to re-compress so it doesn't create "Barrel suck" as it's going backwards.

A trick (Credit goes to Ty) is to take the o-ring, stretch it around the cylinder and heat it up with the HEAT (not flame, HEAT) from a candle or a heat-gun.

The gearbox definately sounds louder then before and there is alot more air being pushed out of the barrel so thats a plus.

Also the ball bearing spring guide is doing its job and pushing the piston back into the cylinder more then before (always stayed pulled back with the old guide) which is another plus.

So I'll probably hit up the chrono later tonight anyways...

The stock Modify oring is too small. Go to home depot, get a 1/4 inch oring and replace the one you have right now. Also, replace the hop up rubber with another one to see if the compression issues (if any) are coming from the hop up. If that doesn't work, your spring may just be weak; get a Modify M110 spring and u should be shooting 390ish fps. U might as well get a Modify portless cylinder while you're at it. My P90 uses 85% of the same parts as yours, there's no reason why it shouldn't be shooting 370+ fps.

1/4 o-ring, is that a bit small?

I'm not 100% sure that that is the correct name for the oring but I can attest to the fact that if u go to home depot and buy the oring that's about the size of a piston head, it WILL provide better compression. Come to think about it, now that i actually measured out the size of a piston head oring, that is too small. I don't know how the measurement works but if u can get an oring close to the thickness of a TM oring then you're good!