Originally Posted by surein
IMHO Leave the valve spring as is and muck around with the hammer spring.
I agree, I spent a lot of time trying to spring tune my Sterling and I found the best results with just messing with the Hammer/Sear spring. I tried to mess with the valve spring but it made less consistent shots.
Thanks to this thread I think my gun is out of tune because I have to have the pressure so high (800 psi) to get 280 FPS, but with what James_Blond said about the main pump rod opened my eyes to think mine needs to be screwed out some because I need to have the Hammer/Sear spring so long (I cut a Spyder Spring) when I unscrew the front frame bolt the spring just pushes out the "pick up assembly" kind of violently. After all the gun hasn't been "timed" since I got it back in the 90's.
So it's back to spring tuning again.
Started with a Splatmaster, moved onto a Nelspot 007, then came the Autocockers, then a STERLING Pump, next was a Bob Long defiant then a PM7. As of now I have 6 Sterling Pumps, 1 Phantom for SC, a CCM SS-25 and a Sovereign 3.