PGP2 suddenly shooting low. Needs new springs?
I've been trying to get my PGP2 back up to snuff and am running into problems.
Assuming I remember everything correctly, the last time before this fall I chronographed the gun it was shooting 280fps with .687 Valken paint. The gun has a Cooper-T pusher bolt and a Palmer's dynavalve valvepin and an autococker grip frame mounted with an adapter plate.
Having changed nothing, last week I shot the gun for the first time in a long time and no matter what I do it won't shoot above 230fps or so. I've tried shimming the mainspring with various things but it seems as though there is a point where if I increase the tension any further the gun will:
1. Refuse to cock
2. Cock, but the bolt won't come back far enough to chamber a ball
3. Refuse to let the trigger move at all (what happens if I cock and chamber a ball, then crank in the velocity adjuster.
Is this happening because the mainspring is compressed all the way and is putting direct pressure on the back of the hammer?
Do I need a new mainspring?
I've tried some different valvesprings as well with no good results. Most of the ones I've tried have been too light and result in the gun freeflowing. I tried a cut-down green 'cocker valvespring and the velocity actually decreased for some reason and efficiency seemed to be halved.
This is really aggravating because the last time I used this gun it could shoot any velocity I needed and I've changed nothing since then. Also, if this has anything to do with the stock frame, I sold it years ago.