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Thread: QB78d long Co2 tube

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    Member just missed's Avatar
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    QB78d long Co2 tube

    Planning on bulking my QB78d and would like to add a longer main tube, more shots and I don't want to cut my new stock. I there a direct fit tube out there, sticking with Co2.

    John

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    Senior Member SeanMP's Avatar
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    Sean

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    I saw this during my search, is there a issue using this tube for Co2?

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    Administrator AirGunEric's Avatar
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    Other than it being twice as strong as it needs to be for Co2, no.
    I'd say I care- but I'd probably be lying...


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    Order placed, maybe one day I'll make the leap to HPA

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    Senior Member SeanMP's Avatar
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    On the QB's it's a really easy leap...more like a tiny step.

    When you assemble the gun just use silicone grease/lube and nothing else. Then switching to HPA is as simple as filling it with HPA.
    Sean

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    Member daguasta's Avatar
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    Quote Originally Posted by SeanMP View Post
    On the QB's it's a really easy leap...more like a tiny step.

    When you assemble the gun just use silicone grease/lube and nothing else. Then switching to HPA is as simple as filling it with HPA.
    is not the pressure limited to 1500 psi tho?
    unless further mods are made?
    Everyone is entitled to an opinion ...but only mine is right!
    DAVE G

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    Senior Member SeanMP's Avatar
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    well I've stretched it as far as 1800psi. The limiter is the hammer/hammer spring. Bob has a fair bit of data on mods and pressures.

    You also want to give the valve to valve stop block clearance a quick check if your planning on going to very high pressures. Ideally this clearance should be as tight as possible. I epoxied a thin shim washer onto my stop block.
    Sean

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    Moderator rsterne's Avatar
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    I would stay under 1800 psi on HPA with a QB.... CO2 can reach that pressure at 120*F, so IN THEORY the gun should be able to handle that.... The problem with regulated HPA is that if you have a regulator failure the gun will see whatever pressure is in the tank.... would could easily be 3000 psi.... even 4500 if you are using a 300 bar Carbon tank.... I would highly recommend that if you are using HPA on a QB that you make sure there is a 1.8K burst disc on the downstream side of the regulator.... That limits you to about 1500-1600 psi so you won't blow the disc.... If you are only filling with a hand pump, I might consider using 1800 psi.... but you will need to shim the hammer spring, replace it, or increase the hammer strike in some way to use that much pressure....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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    .177 Diana 34, 1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 22XX PCP 8-shot Carbine, 2260 PCP Rifle (50 FPE), Hayabusa PCP, .22 B-26, DAQ .308 Exile

  10. #10
    Senior Member SeanMP's Avatar
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    Bob, I think the question was what do you have to do to utilize the full potential of the aftermarket 3000 psi tube. I can't comment on any specifics beyond the stock tube
    Sean

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