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All Springer/NP/PCP Air Gun Discussion General > Vintage Air Gun Gate

doesn't release all the air when shot

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bob noffs:
my last post was after a reseal job of my ben. 312 and the gun wouldn't hold the air pumped into it. i cocked it before pumping and that seemed to help. after i put a new seal in the pump mechanism and oiled it it seemed to work. but it does not shoot as hard as it did with the old seals [50 yrs old] after i shoot i cock it and shoot again with no pumps and it discharges more air. so the hammer isn't opening the valve long enough? i really don't know what's going on, i would appreciate any suggestions.
 bob noffs

Rob112o:
The first issue makes it sound like you have an overly heavy hammer spring. When you say "cocking it first seems to help". Yet, you also state you can cock again and discharge without pumpkin. Which would mean the opposite you have a weak hammer spring. Another reason for excess air left is the valve spring is too heavy. Remove valve spring and replace with a weaker spring or compress the current valve spring till coils bind and hold for an hour or 2. Cocking, CAN'T "seemed" to help. It will either helped or it didn't. When you cock rifle the hammer no longer is pushing on the valve stem.
  This sentence: "my last post was after a reseal job of my ben. 312 and the gun wouldn't hold the air pumped into it." Was this the previous issue that you where having and that's why you resealed the rifle? If not I'm at a loss for words. In that whole paragraph you wrote your rifle is having issue that it shouldn't be having because of what you wrote...Conflicting issues. I can't give you a clear answer because your thoughts are scrambled.

bob noffs:
i reread my post and it pretty much says what is going on but i will rewrite it and maybe it will be clear.
 ben. 312 is 50 yrs old and before i did the reseal is held air and shot hard [my chrono is broken]. after reseal of the valve and 2 new valve springs it would leak out the air as fast as i would pump it. definitely sounded like it was coming thru the bolt. someone suggested i cock it before pumping so i did and then it held air.at that time i also oiled it well so maybe that was a factor.
 then i took the pump arm apart and replaced the cup that pushes air into the chamber.after gun was back together i shot it and it does not shoot nearly as hard as it did before i resealed it.
  then i pumped 6 times and shot a pellet. it was weak. without pumping any more i recocked it and pulled the trigger and more came out.
  i hope this is clearer now. so maybe new valve springs are too strong or hammer spring is too weak against new valve springs? or maybe when it wouldn't hold air it wasn't the springs at all but some other cause of leak?
 i am looking for advice as the best way to get all the air to release at this point.
 bob

Hoosier Daddy:

--- Quote ---so maybe new valve springs are too strong or hammer spring is too weak against new valve springs?
--- End quote ---

This sure sounds like the case to me Bob... It is easier to give the hammer spring a stretch and see if that corrects it. You don't have to go deep into it again doing that.
 But if you go too far you may be back to the point of needing to cock it before pumping again. I have learned it is a pretty fine balance between just right and too much.
 Did you clean everything well when you had it completely apart?

bob noffs:
yes, i cleaned as well as i could. the valve seat i replaced was terribly crutty , looked like something out of an old water heater.can't believe it worked fine.
 can you give me an idea of how much to stretch? i mean like 1/32'' or closer to 1/4''.
 bob

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