Help! Need more power from my Gamo Urban

Forums PCP Airguns PCP Airgun – Discussion Help! Need more power from my Gamo Urban

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    Slash91
    Participant
    Member

    @prfssrlwe

    Do I need an extra long 4mm Allen wrench? I tried with a typical 2.5″ long tool and couldn’t feel any screw in there. I am so blind I could not see anything in there, either. 

    Thanks.
    Chris 

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    keithhibbert
    Participant
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    @prfssrlwe

    ​looking to achieve similar power. What size is your transfer port? Wondering if I might have to open mine out a bit.

    Cheers
    Keith

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    prfssrlee
    Participant
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    Hi Keith, My gun is completely stock. Only thing I did was turn the hammer spring pretension screw. good luck!

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    Slash91
    Participant
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    Thanks for the new replies. 

    I have no clue what size the transfer port is. I tried to tighten the screw a few people have mentioned but mine would not budge in either direction. 

    My willingness to take this thing apart may not be up to that of many contributors here on this forum. 

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    PPP
    Manufacturer
    Manufacturer

    Hi Slash91,

    By far the biggest gains in power would be from the transfer port size, valve volume, hammer spring tension and barrel length…probably other things too, but these are the main culprits in when looking for ways to increase power.  I also recommend a regulator as it will produce consistency (regulator chamber volume, or plenum space also matters if you add this option).  In your case the transfer port and the barrel port must match up to to at least 4.5-5.0mm in diameter, preferably closer to 5.0 mm for the biggest gains in power.  Remember the pellet has to slide over the barrel port, so it can’t be too big or the pellet will get damaged.  The valve should not be restricted in any way, some bsa valves (not sure if yours does or not) have an insert that takes up valve chamber volume.  This should be removed or volume chamber increased by machining more space into the valve.  You can choose a heavier hammer if needed, but the stock hammers are usually enough to produce high power (30ftlbs+) in a .22 caliber with a little tweaking of the tension screw.  Just doing these mods should put your JSB 18 grainers @ 900fps or more.

    By doing these mods and adding a regulator you can make the gun shoot anywhere from 12ft/lb (or lower) all the way upto full power. Changing springs thickness, regulator pressure, and volume spaces gives a lot of control!

    Nick
    precisionpneumaticproducts.com

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    kingston73
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    I thought about starting my on thread but it seems like my question fits in here.  Going to opposite direction, will lower power give any significant gains on shot count?  I bought my urban used ski don’t know of the original owner changed anything but I get about 30 shots before the POI starts to change.  I mostly target shoot and haven’t shot at anything larger than an English sparrow but want enough power to safelykill a raccoon if needed.   No chronograph so I don’t know what speed I’m shooting right now.

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    Td2hi
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    Member

    Hello I'm new to the site, being as I just purchased a Gamo Urban at auction for $90.00 US. I am looking for information and tips on set up and tuning, and the best type of ammo to use for hunting small game. I live in California 😭 so I have to use non lead pellets. thanks

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    PumaCarl
    Participant
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       Td2hi, go to the Hunting forum on this website and read the thread "Hunting In California", it would seem that you can use lead pellets in Cali with airguns for hunting.

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