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-   -   PGP2 suddenly shooting low. Needs new springs? (http://www.mcarterbrown.com/forums/sheridan/220285-pgp2-suddenly-shooting-low-needs-new-springs.html)

The Inflicted 12-04-2012 04:45 PM

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.

The Inflicted 12-04-2012 05:38 PM

Just realized that fully tightening the sections of my cartridge valve results in the exhaust port being out of alignment. Is there a way to ensure that the alignment is correct before inserting the cartridge?

WALZ 12-04-2012 08:48 PM

One easy way to align the valve port hole is to screw in the grip screw at the front and insert into lower tube as far as it will go. Now simply align top hole with center of tubes. Pull out and mark with scribe or sharpie.
Should do the trick...

The Inflicted 12-05-2012 03:08 PM

Ok, I think we're in business with the exhaust port alignment.
I screwed two bolts into the ports so that I could get them inline, the re-checked once the valve was in the gun.
It's shooting up to 276 with a fresh cartridge now, and won't go any higher without binding the hammer, but this is with very small (0.677 ?) paint and fairly rapid shooting.
Thanks for the help, Walz!

http://s12.postimage.org/ppvhu5ot9/pgp_003.jpg
upload


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