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 Post subject: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 9:25 am 
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Joined: Mon Jul 24, 2017 4:59 pm
Posts: 32
Hi all, just bought a used qb chief through a member here, found one issue is if let the gun sitting for few hours or longer, the first 2-3 shots feels low power, then it will back to normal. I can tell from dry fire, the sound is much quieter for the first few shots.
Any idea what could be wrong or this is normal?
Thanks

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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 10:07 am 
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Joined: Mon Aug 15, 2016 11:00 pm
Posts: 604
probably you'll need a regulator if you don't like this low 2 shot initial, what's happening I think is sitting for a while is causing the pressure in the plenum chamber and the tank pressure to have a equal pressure, that is adding pressure to your valve pin besides the spring pressure, this is causing that low exhaust in your first 2 shot, because of the equal pressure from your tank and plenum chamber.


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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 10:15 am 
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Joined: Mon Jul 24, 2017 4:59 pm
Posts: 32
pistolero wrote:
probably you'll need a regulator, what's happening is sitting for a while is causing the pressure in the plenum chamber and the tank pressure to have a equal pressure, that is adding pressure to your valve pin besides the spring pressure, this is causing that low exhaust in your first 2 shot, because of the equal pressure from your tank and plenum chamber.
Thanks for the advice. So does it mean it's normal for a non regulated pcp, such as stormrider, maximus etc.?
As I was thinking take it for grouse hunting this year, and so I either install a regulator, or dry fire 2 shots before aim a grouse when I see one:) , if it's still there:))


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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 10:44 am 
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Joined: Mon Aug 15, 2016 11:00 pm
Posts: 604
yes its normal for a non regulated, it happens to my cr600w if I pressurized the tank to about 2500psi, need to relieve that plenum pressure, if I pressurized it to 2000 psi, it was behaving normal and not need to waste some air to reach that pressure. its basically up to you on how you like to use the gun, either you find that ideal pressure in the tank or add a regulator.


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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 1:25 pm 
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Joined: Mon Jul 24, 2017 4:59 pm
Posts: 32
pistolero wrote:
yes its normal for a non regulated, it happens to my cr600w if I pressurized the tank to about 2500psi, need to relieve that plenum pressure, if I pressurized it to 2000 psi, it was behaving normal and not need to waste some air to reach that pressure. its basically up to you on how you like to use the gun, either you find that ideal pressure in the tank or add a regulator.
Appreciate your help. [emoji111]

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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 3:10 pm 
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Joined: Mon Jul 24, 2017 4:59 pm
Posts: 32
pistolero wrote:
yes its normal for a non regulated, it happens to my cr600w if I pressurized the tank to about 2500psi, need to relieve that plenum pressure, if I pressurized it to 2000 psi, it was behaving normal and not need to waste some air to reach that pressure. its basically up to you on how you like to use the gun, either you find that ideal pressure in the tank or add a regulator.
By the way, is there any recommendation for the regulator? I see one on the Ebay around $120.
Thanks

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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 5:27 pm 
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Joined: Mon Aug 15, 2016 11:00 pm
Posts: 604
try Wes of airgunarchery.com, its cheaper than ebay, send him a pm, I think the Altaros regulator will fit your QB Chief, double check with him for the diameter and counter check yours internal diameter of your airtube, because I know that this will fit a discovery as they have the same inner diameter for the discovery and the cr600w.
https://airgunarcheryfun.ca/altaros-reg ... 00w-pp800/


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 Post subject: Re: Qb chief creep issue
PostPosted: Sat Sep 19, 2020 5:59 pm 
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Joined: Mon Jul 24, 2017 4:59 pm
Posts: 32
pistolero wrote:
try Wes of airgunarchery.com, its cheaper than ebay, send him a pm, I think the Altaros regulator will fit your QB Chief, double check with him for the diameter and counter check yours internal diameter of your airtube, because I know that this will fit a discovery as they have the same inner diameter for the discovery and the cr600w.
https://airgunarcheryfun.ca/altaros-reg ... 00w-pp800/
Thanks. Will do.

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 Post subject: Re: Qb chief creep issue
PostPosted: Mon Sep 21, 2020 11:28 pm 
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Joined: Sat Nov 05, 2016 10:52 am
Posts: 3630
Location: Caronport, Saskatchewan
I do have a Lane Regulator for the Chief. It's a lot bigger diameter than a Discovery or Stormrider. But I think you'd just be better off filling it not quite so full, a few 100 psi less and you'll be in the sweet spot. However just a warning that quieter doesn't always mean less velocity. The fact is your gun is more efficient at the top end of the pressure and the Valve is closing before the pellet gets to the end of the barrel making the gun a lot quieter. This can be deceiving because it can actually be going faster when it's quieter than when it's louder. Of course if the pellets are dropping more then you're right, it's overpowering the hammer spring too much and you're losing power. A chronograph is always a very handy tool to see what is really going on.

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 Post subject: Re: Qb chief creep issue
PostPosted: Tue Sep 22, 2020 10:15 am 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 9206
Location: Coalmont BC
While a regulator is one solution (and a complete retune to go with it).... you have two other choices.... You can fill to a lower pressure so that you don't experience the low velocity on the first few shots (since they are unusable anyways).... or you can increase the hammer spring preload until you move the bell-curve up.... You want a velocity on the first shot about 4% below the peak, and then when the velocity drops 4% below the peak at the end of the string, stop shooting and refill....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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