My Artemis LR700W whistling when shooting

[Ultramarine]

Now I'm getting used to the Artemis LR700W I bought some monts ago and I can get decent groups at about 20 yards with iron sights, and pleasant plinking shots at 32 yards.

But from the beginning, this rifle has always had its bolt jumping when shooting. First I didn't pay attention to it but today something new happened : at the same time I shoot, I can hear a very short hissing or whistle, hardly longer than the shot sound itself. So I supposed there must be a wrong O'ring somewhere and I began disassembling the rifle. A bit tricky, regarding my tinkering abilities... I recommand you the small steel pins on the trigger blade. Well, I eventually  just could see the two O'rings of the exaust valve and they looked perfect. If I consider the LR700W inner parts as quite similar to the Artemis pr900W ones (http://spares.bagnallandkirkwood.co.uk/artemis/artemis-pr900w-pr900-air-rifle-spare-parts/), there's quite a lot of other O'rings to be checked. But I feel I reached my limits and I don't want my tinkering to make that air rifle unusable.

So my question is : has some of you, good fellow members, changed any O'ring on an SPA LR700W, a Seneca Dragonfly or... a Diana Stormrider, as I think all these rifles are manufactured on the same SPA basis. Do you have any opinion about the O'ring that may cause that "jumping bolt" and that brief whistle, and do you know the best way to reach it  with the less possible hassle ?

[Motorhead]

Likely the regulator refilling plenum .... many of the low flow type regs make a low tone Wheeze sound while recharging plenum pressure.

Just a WAG tho ...

[Ultramarine]

But it's a MSP, a pumper to be short, not a PCP! Any regulator on a MSP ?

[Motorhead]

But it's a MSP, a pumper to be short, not a PCP! Any regulator on a MSP ?

Nope .. my bad

MSP ... could just be the valve IS NOT doing a full dump shot and what your hearing is the some of the air weeping by the poppet once nearly closed again.. WAG once more

[Ultramarine]

I'm going to explore that, but how... I have no chrony so I can't tell if there's actually any significant air loss.  Anyway that hissing is disturbing.
I can't find it back but I'm sure I've read on GTA someone's info about the cause of a bolt jump on an MSP ; and that it was related to an O'Ring. Which one, I can't remember.

[Back_Roads]

 Possibly the bolt probe o ring ? I will go look at mine to see if it even has one LOL and report back.

[Back_Roads]

 OK the bolt probe must have an internal oring, as I see no place for one on the probe. But as I was thinking about this, I came to a conclusion that it may be air trapped in the area between the valve and the pump cup, replenishing the valve as the valve pressure is depleted. it may not have enough force to close the valve, like a full pump would in recharging the gun.

[Bentong]

The bolt probe gets it's seal from the o ring that's behind inside the barrel. See if there's a blast of air when you shot it by placing the back of you're  hand. If it's leaking, you need to pull the barrel to replace. Barrel got 2 skinny o ring that easily get cut. Shoot it with the single tray with then without pellet to easily feel if leaking from there.

[Ultramarine]

I don't know if the probe is the right track, as I've seen many reports of "jumping probes" on GTA not related to any leak. Anyway, I made my own test, the "talc one", a bit dirty but quite sensitive as you can  imagine. Very little air escaping from the breach.
But I have another clue : usually, when I forget to cock the rifle before pumping, which happens from time to time because neither my Crosman 2100 nor my Webely Rebel clone requires it, there's a kind of burp, fart or whatever you'd call it, as the pump handle is about to be closed and the effort to pump suddenly disapears. Now, no more of those uncongruous sounds and quite no effort to pump if the rifle isn't cocked, even at the beginning of the stroke. So I'm going to look around the pump O'rings and even its cup.
I'll tell you...

[Ultramarine]

I just failed .
Spent a looong time to disassemble the rifle farther than the last time I did, with the help of the Seneca Dragonfly exploded view (https://www.pyramydair.com/air-gunsairsoft-schematics).  Badly jammed one of what they call "air reservoir stopper screw" (piece n°26 in the scheme) so that I couldn't remove the pump. Disassembled the hammer and its piston screw, could push as forward as possible the"air reservoir mount" so to be able to check the valve connector and its 2 O'rings (still in good shape) but could not reach the exaust valve and its accessories.
May be it's better because I went half mad with all these small pieces and, at least, I only damaged one screw.
Then I succeeded reassembling everything, which is a kind of performance for me. I'm reluctant going farther as I feel it would be  wayyy beyond my tinkering abilities. So I'll have to cope with a whisting pumper for a while .
There's just NO airgunsmith in  France whom I could expect any usefull help from. Would he exist, he'd probably ask me the rifle's price for a dubious result..

[Ultramarine]

Third attempt to reach the valve failed, again>

By no means could I disassemble the intake and exhaust valves. I tried pushing all the mechanism  on both sides with a wooden dowel but it wouldn't move, so I didn't insist. Moreover, there's a deep transversal mark in the pump tube just where the valve mechanism is located that makes me wonder if its not a kind of swaging that once for all prevents the valve to be removed (see pic here attached) .I can hardly believe it, for the manufacturer would not provide spare O'rings, as he does,  if you couldn't use them.

So, an Artemis LR700W being quite exactly the same as a Seneca Dragonfly, has anyone here disassembled this rifle so to be able to reach the intake and exaust valves and remove its O'rings ?

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(BTW, this post has been removed from the Chinese aigun gate and put here but an SPA or Artemis LR700W isn't a PCP, just a multi-stroke pumper,  so may be it would be better to put it back to the Chinese gate...)