Kalibrgun Cricket tactical regulator seat and air flow hole ?

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mubhaur

mubhaur

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Nov 8, 2015
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Just disassembled the Cricket original regulator. It was not working fine.

Found that O rings had gone bad and regulator seat of black (perhaps) delrin had developed a round deep circle on the center of the delrin tip.

The metal part that touches the delrin to stop air has quite a large round hole with a bit thin edges.

Polished the delrin to look like new and removed the round impression.

After replacing O rings, and setting the reg pressure, reinstalled the regulator.

Regulator is working good but one thing is very odd that even if I leave the gun for 10 minutes the fps drops from 935 fps to 880 fps. Then after a couple of shots it comes back to 935fps.

I dismantled the regulator again to see the effects on mating surfaces.

Surprisingly with just 100 shots the newly polished delrin seat had again developed a round circle impression of the other part from where the air comes.

Nothing felt sharp. Assembled the gun again but the behaviour is same that even after a few minutes, the gun shoots two shots slow.

To me its acceptable if gun is kept overnight. But just leaving it for a few minutes, so much drop in fps is worst thing for a hunter.

Please advise if I should take it that once the regulator will be broken in, the problem will be fade out or there is something else that I need to do ?

Regards

Bhaur
 
Before I move to the subject of the regulator seat, are there other potential causes that need to be considered? For example are there any O-rings associated with the operation of the valve that are potentially causing stiction? Either a balanced valve or a conventional valve with an O-ring on the stem?

Regarding the seat and potential pressure creep, it's certainly possible that it simply isn't fully broken in yet and will cease to creep when the material fully takes on an imprint of the cone. However in cases where both the apex of the cone and the plastic have been carefully surfaced and polished, it usually doesn't take long for it to settle. At least with a medium-hard plastic like Delrin. For example, a reg I rebuilt just this past weekend (Huma clone/floating disc type) was good after a brief session of just 30 pellets. Whereas hard materials like PEEK or PEI may take longer...maybe never if there's the slightest imperfection :)

If in your estimation the indentation is excessive for having been cycled only ~100 times, you may want to consider blunting the cone ever so slightly (and/or swap to a harder plastic). There's a fine line between too sharp and too blunt so you'll have to make a judgement call. BTW after polishing the apex of the cone, I like break the sharp edge on the ID of the orifice, at least in cases where the orifice is big enough to hit with a small conical diamond bit. That step is for longevity...I don't expect it makes any difference with initial break-in.

Lastly, I didn't see it mentioned but is the hammer strike adjusted for the velocity knee?
 
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nervoustrig said:
Before moving to the subject of the regulator seat, are there other potential causes that need to be considered? For example are there any O-rings associated with the operation of the valve that are potentially causing stiction? Either a balanced valve or a conventional valve with an O-ring on the stem?

Regarding the seat and potential pressure creep, it's certainly possible that it simply isn't fully broken in yet and will cease to creep when the material fully takes on an imprint of the cone. However in cases where both the apex of the cone and the plastic have been carefully surfaced and polished, it usually doesn't take long for it to settle. At least with a medium-hard plastic like Delrin. For example, a reg I rebuilt just this past weekend (Huma clone/floating disc type) was good after a brief session of just 30 pellets. Whereas hard materials like PEEK or PEI may take longer...maybe never if there's the slightest imperfection :)

If in your estimation the indentation is excessive for having been cycled only ~100 times, you may want to consider blunting the cone ever so slightly (and/or swap to a harder plastic). There's a fine line between too sharp and too blunt so you'll have to make a judgement call. BTW after polishing the apex of the cone, I like break the sharp edge on the ID of the orifice, at least in cases where the orifice is big enough to hit with a small conical diamond bit. That step is for longevity...I don't expect it makes any difference with initial break-in.

Lastly, I didn't see it mentioned but is the hammer strike adjusted for the velocity knee?
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Good point but this Kalibrgun has are no O-rings associated with the valve that would cause stiction. The seat is Delrin. Mubhaur isn't at all new to tuning a PCP.
 
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Mating surfaces are square as the impression of metal part in the delrin is a fine circle with visually equal depth of 360 degrees.

I hope it will settle as it breaks in.

I would like to make a change in the regulator if this gun had been mine.

I would remove the adjuster screw that is made of delrin and make a new adjuster out of brass with a peek seat.

I understand it will be an improvement to the regulator.

Bhaur
 
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