Walther LP-3 question.

[Crank]

I picked up a Walther LP-3 at the Placerville show knowing that the seals we're shot. I cleaned everything up and the new seals arrived today. I put it together and it pressurizes and fires. However, it's not a powerhouse in the first place, but I noticed it had an unusual quirk. As the lever is completing the very last portion of the stroke, I could hear a small brief hiss out through the barrel. 

I'm going to leave it with a charge of air to see if it leaks otherwise, but it seems like that last bit is the key to a bit more velocity. 

Has anyone observed this issue on their own LP-3? I'm not terribly distraught over it, but I would like to see if it is a correctable issue. 

I'm posing the question here on the odd chance that it is some funky factory design to regulate the pressure to a given level for competition. Thanks in advance.

Of course I will add the obligatory photos as proof it exists.

Yes, the receipt shows it was sold in Germany.

Thanks



Mark

P.S. I just checked it and it still had air after about 25 minutes. 

 

[AirNGasman]

Lovely LP-3; I love 'em!

Chronographing your LP-3 would give you a good idea what you're losing. Healthy examples should get about 350 FPS with pellets around 7 grains, and about 300 FPS with pellets around 8 grains.

 

[Crank]

AirNGasman,

Thanks for the velocity figure. I have to dig out my chronograph and hope it will see the pellet. It's still holding a charge over 24 hours and doesn't seem any weaker. I'm wondering if the new urethane valve seal needs time to settle in to handle the spike in pressure at the last portion of the compression stroke. Not a terrible worry yet. I'll see what I can find out.

Thanks

Mark

P.S. I just thought about the seal at the compression tube to the breech. The o-ring I used there could be a weak point. I may look into a thicker one there if this persists. I'm just leaning towards the valve because I distinctly hear air out of the barrel, not the action.

 

[Crank]

I chronographed it and it was running about 160fps. I took it apart and realized I had done a Bozo manuever. There are two springs that are different by one coil. One is the valve spring and the other is for the valve release. I swapped them, it went to 300fps for two shots and went back to leaking. So it looks like the spring has seen better days, l'll see if I can get a stronger spring. Hopefully that will put it back to full function. 



Mark

 

[Crank]

Well, I made a spring with a larger coil thickness and it still was acting up. I decided to try inverting the valve seal "wrong" (the un-bevelled side towards the ball) and it works. Velocity is right at 300fps and it's holding air. 



Mark