Shutter shooting way too fast

[aerosaaber]

I have a Shutter (it's actually a mechanical shutter trigger frame on an e99 avant body). I got it used and tore it down, replaced the o-rings and got an upgraded spring set. I'm 99.99% sure all the parts went back to where they belong. The bolt came out of the shutter but the rest of it is original to the e99.
I took it to the chrono at the field and it was shooting like 400fps on CO2. The CO2 tanks had been in the car, but not by a heater and the weather was chilly (like 40-50 degrees) so I don't think the tank was at super high pressure.
I adjusted the velocity knob, no real change. Someone suggested I remove the knob completely, so I tried it without any real change.
I read something on another thread or forum that says maybe the spring is too strong. The kit I got had 3 springs but I don't remember which one is in there.

Any ideas?

Do I need to swap the valve assembly from the e99 for the one from the shutter?
Do I need a softer spring? (the one I put in might be the middle spring or the strongest one)

I'll be back at the field this weekend and I'm gonna try using HPA instead of CO2 and maybe try swapping the springs around.

[oldironmudder]

Swap out the main spring for a softer one. If you are still shooting hot with the adjuster out, clip a ring or two off the spring & retry.

[aerosaaber]

Alright, I'll give that a try, I won't be able to try it until Sunday so any other ideas please post them up!

[Hob Hayward]

Thats prettymuch all there is to it, you could also try a stronger valve spring if your spring kit them.