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Thread: Ailing Airsporter

  1. #1
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    Ailing Airsporter

    Or is it?,a recently acquired S model producing around 650fps with 7.9grn accupels.

    The mainspring appears standard and in good nick at around 250mm and 33 coils.

    The piston head has a new replacement seal and decent buffer fitted.

    But the pellets do seem to be a rather loose fit in the loading tap.

    Any thoughts,or indeed input, would be much appreciated .

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    Mercurys and Airsporters often suffer from 'O' rings which are too tight a fit in the compression chamber bore. The cure is to fit the smaller 'O' ring from the BSA Meteor, or if you have a collection of 'O' rings, one which is not such a tight fit. Also, the 'O' ring has to be in good condition, it is easy to knick them as they are fitted. Use old-type camera film to ease the 'O' ring in. If the spring is in good condition and the piston seal is sealing and a good fit, you should get between 10.5 and 12 fpe depending on pellet from an Airsporter in .177. I think the later S model increased power by using a steel piston head - less bounce with a stronger spring perhaps. As you say, it might be an idea to try some other pellets, JSBs, H&N FTT and RWS Superfield would be my first choices.

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    Thanks bud,the seal on the metal piston head came out of our air-con. selection box and is a nice sliding fit.

    As you suggest it might be an idea to test a range of pellets to find one that fits snugly in the breech plug.

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    Quote Originally Posted by piggy589 View Post
    Thanks bud,the seal on the metal piston head came out of our air-con. selection box and is a nice sliding fit.

    As you suggest it might be an idea to test a range of pellets to find one that fits snugly in the breech plug.
    Other than the seal, if it is still a problem then there is a chance the tap is misaligned - shoot into some loosley packed cotton wad or something that wont deform the pellets and see if they are going into the bore squarely. Check that the piston rod is straight. GOod luck !

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    I made a point of looking through the stripped action from the rear to check the tap alignment.

    All appeared to be correct,there again there's nothing to say the tap to action gap isn't allowing air to escape.

    From memory this is acknowledged as the Airsporter's achilles heel,a flawed design.

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    Use a dome ended pellet probe to seat the pellet in the bottom of the loading tap, I've found this improves consistency and power on all my tap loaders.

    DaveM.

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    Airsporter-......lack of power

    Quote Originally Posted by DAVALI View Post
    Use a dome ended pellet probe to seat the pellet in the bottom of the loading tap, I've found this improves consistency and power on all my tap loaders.

    DaveM.
    try lubricating the loading tap with thick silicon grease, If it is like my Mark 1 ensure the little spring in the ens of the loading tap is strong and in good condition

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    Thanks fellas,in an old post someone suggested using BSA's own Storm pellets, as they raised the power of his old tap loader from 7 to 10ft/lbs.

    Presumably a snug fit in the tap and bore .

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    Quote Originally Posted by piggy589 View Post
    Thanks fellas,in an old post someone suggested using BSA's own Storm pellets, as they raised the power of his old tap loader from 7 to 10ft/lbs.

    Presumably a snug fit in the tap and bore .
    There is no way that a crap pellet should lose you more than three fpe. The Airsporter S should do well over 11 fpe in .177, not 7.5. Just look at the size of the compression cylinder and the spring, my HW30 does 7.5 fpe in .177 and that is a midget compared to the sporter. The bore is the same in .177 as now, it is only the .22s that are slightly over, and even then it is a matter of accuracy rather than power that suffers. Something is seriously out of kilter with it. Try using RWS Superfield and have another look at the piston washer.

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    Quote Originally Posted by Chippy65 View Post
    try lubricating the loading tap with thick silicon grease, If it is like my Mark 1 ensure the little spring in the ens of the loading tap is strong and in good condition
    Absolutely DO NOT use silicone grease on the tap, it will cause it to gall and then seize solid. Believe me, I know. If you don't, then read this thread all the way through ...


    http://www.airgunbbs.com/showthread....silicone+seize

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    Quote Originally Posted by Hsing-ee View Post
    There is no way that a crap pellet should lose you more than three fpe. The Airsporter S should do well over 11 fpe in .177, not 7.5. Just look at the size of the compression cylinder and the spring, my HW30 does 7.5 fpe in .177 and that is a midget compared to the sporter. The bore is the same in .177 as now, it is only the .22s that are slightly over, and even then it is a matter of accuracy rather than power that suffers. Something is seriously out of kilter with it. Try using RWS Superfield and have another look at the piston washer.
    Cocking the gun with the loading tap open and then closing it produces a hiss as air is drawn into the vacuum created.

    Suggesting to me the new replacement piston seal is doing its job.

    As you say the swept volume alone should produce over 11ft/lbs.

    Hell,I've got a couple of sixties Meteors,.22 and .177, both nudging 11.

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    Quote Originally Posted by piggy589 View Post
    Cocking the gun with the loading tap open and then closing it produces a hiss as air is drawn into the vacuum created.

    Suggesting to me the new replacement piston seal is doing its job.

    As you say the swept volume alone should produce over 11ft/lbs.

    Hell,I've got a couple of sixties Meteors,.22 and .177, both nudging 11.
    The seal might be good but one Mercury I had was the same, a good seal but the friction of the O ring was slowing the piston down a great deal. The other thing is that sometimes they can be over-sprung, causing piston bounce which reduces power. It's a conundrum to be sure. The game is not helped by the unpleasantness of stripping them and building them, always found them the most difficult to re-spring due to the odd shaped back block and the amount of preload they have.

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    my mk 2 does 100 fps less with jsb pellets than it does with superdomes its .177

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    Quote Originally Posted by Hsing-ee View Post
    The seal might be good but one Mercury I had was the same, a good seal but the friction of the O ring was slowing the piston down a great deal. The other thing is that sometimes they can be over-sprung, causing piston bounce which reduces power. It's a conundrum to be sure. The game is not helped by the unpleasantness of stripping them and building them, always found them the most difficult to re-spring due to the odd shaped back block and the amount of preload they have.
    A friend who seems to have some success tuning older guns thinks it's over sprung.

    He suggested fitting a lower power spring,but also adding a piston weight.

    Sounds good,that trigger block is indeed a swine to fit.

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    Quote Originally Posted by Chippy65 View Post
    try lubricating the loading tap with thick silicon grease, If it is like my Mark 1 ensure the little spring in the ens of the loading tap is strong and in good condition
    I had a brilliant Airsporter 'S' till I lubed the tap with silicon grease-three shots later and the tap had siezed solid....gun ruined forever.

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