Classic Army CA90 TR and Modify Springs

[Cokeman]

I just recieved my Classic Army CA90 TR on Friday. It came with a M140 spring. So, it was time to do some downgrading - with the goal to get as close to 380-390 fps. All tests were done with an 8.4 v 100 mAh NiMh battery. Here are my results:

Stock spring (included as a "downgrade spring"): 350-360 fps
Modify S100+ Spring: 340-350 fps
Modify S110+ Spring: 350 fps
ICS M120 Spring: 405 fps (7.6 rounds per second)

Stock spring with an Army Force bearing spring guide: 370-380 fps

So, I'm sticking with the stock spring with the bearing spring guide.

A few questions:

1. Why did the Modify S100+ and S110+ springs give essentially the same fps?
2. I tried the same Army Force bearing spring guide in my friend's King Arms M4 (with the Modify S110+ spring) and it didn't affect the fps at all. Yet, with my CA90 stock spring, it increased velocity by 20 fps. The CA90 stock spring was an inch shorter than the Modify and had uniform coil spacing. Can anybody shed some light on why the bearing spring guide had an affect on the CA90 but no effect on the KA M4?

[THe_Silencer]

You may have a dud. Modify S110s usually give my aegs 390ish FPS.

[L473ncy]

Probably mispackaged from factory? That's the only thing I can come up with. Have you tried testing the springs by compressing them with your hands? If they're more or less the same it could just be mispackaged.

I got an S110+ in my rifle and it give me a pretty consistent ~394-397 using a chrono.

[MaciekA]

I have a Modify S110+ in a V3 gearbox shooting at 407fps.

I think you could have introduced a leak while installing the spring.

A few things to check..

- Piston o-ring. Make sure it makes an awesome seal. If not, stretch it with fire or replace it with one of those nice MASK ones Jugglez sells on airsoftparts.ca

- Make sure your hopup is pressed against your gearbox when the gun is assembled. I'm not familiar with P90 / version 6 hopups, but if there's any way you can increase the tension of your hopup against your gearbox so that the nozzle makes a tighter seal against the bucking lips, do it.

- basic sanity checks: turn off hopup while chronoing, use 0.20g BBs

[Short Round]

Originally Posted by THe_Silencer

You may have a dud. Modify S110s usually give my aegs 390ish FPS.

I got a dud when I first purchased a Modify S110.

Purchased and had a S120 installed, I only get 370fps however someone told me its due to the barrel length, so I am not too worried, plus as long as your above 350, I'd say your fine.

[HKGhost]

Did you put in the spring the correct way? Having it in reversed would give it a lower fps. Check the tension between the S100 and S110 to see if they feel the same.