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Thread: BSA Mercury

  1. #1
    Join Date
    Dec 2012
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    BSA Mercury

    After 50 odd years of being a confirmed air rifle nut...I have never taken a Mercury apart.
    This one is from the early '70's and never been apart...I know the original owner who bought it new in 1972.
    How much pre-load should I expect when unscrewing the trigger block....which is now....at last and with assistance free and revolving/unscrewing nicely.

    BTW its sees to be suffering from a perished seal and buffer washer as it sticks quite horribly when trying to cock it.


    Many thanks in advance from the learned members.

    Cheers Steve

  2. #2
    Join Date
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    I stripped and resealed mine a couple of weeks ago. The buffer washer and breech seal had perished and the O ring had a piece missing (I suspect from being stuck to the cylinder bore as it hadn't been cocked for quite a few years). Pre load on disassembly was quite low, with a little pressure on the end block I was able to control it quite easily. Reassembly was a little more difficult as I didn't want to use a spring compressor in case I damaged the paint on the end block. I had to get my missus to hold the rifle upright with the barrel resting on a piece of carpet and use my considerable bulk to compress the spring and reattach the end block. Took me a couple of goes and a few sweary words to get the thread started but managed in the end

  3. #3
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    Quote Originally Posted by ken69 View Post
    I stripped and resealed mine a couple of weeks ago. The buffer washer and breech seal had perished and the O ring had a piece missing (I suspect from being stuck to the cylinder bore as it hadn't been cocked for quite a few years). Pre load on disassembly was quite low, with a little pressure on the end block I was able to control it quite easily. Reassembly was a little more difficult as I didn't want to use a spring compressor in case I damaged the paint on the end block. I had to get my missus to hold the rifle upright with the barrel resting on a piece of carpet and use my considerable bulk to compress the spring and reattach the end block. Took me a couple of goes and a few sweary words to get the thread started but managed in the end
    Many thanks for this...I can see that I will have to have my H&S hat on.

    Cheers Steve

  4. #4
    Join Date
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    You can get a feel for how much pressure is in there by unscrewing it a couple of turns and lean on it, I put a pair of leather gloves on the end block and put the muzzle on a block of soft wood. You should be able to feel it move it the threads a slight amount when you have leaned on it enough and gives a good gauge as to how much pressure is in there. It’s normally harder to put it back together than getting apart.

  5. #5
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    Hi Weasle, replied to your post of the same in the General Section.....

  6. #6
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    Replacing the trigger block without a spring fitted can help in that you know where the two threads engage when under load

  7. #7
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    Feb 2012
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    Beith
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    Also a lot easeier with the barrel removed, won't stress the breech jaws as much.

  8. #8
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    Quote Originally Posted by piggy589 View Post
    Replacing the trigger block without a spring fitted can help in that you know where the two threads engage when under load
    Nice tip, I never thought of trying that before reassembly

  9. #9
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    Hi Gents

    Many thanks for all the hints and tips....

    Cheers Steve

  10. #10
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    Quote Originally Posted by piggy589 View Post
    Replacing the trigger block without a spring fitted can help in that you know where the two threads engage when under load
    Tried this today and it really works, makes reassembly much easier when you know where the bite point is. Thanks again

  11. #11
    Join Date
    Sep 2018
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    Just been shooting my .22 Mercury S in the garden , shooting lovely

    Pretty good with the modern wasps as well.

  12. #12
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    Quote Originally Posted by Steve Zodiac View Post
    Just been shooting my .22 Mercury S in the garden , shooting lovely

    Pretty good with the modern wasps as well.
    I bought a virtually unused Airsporter S many years ago and it sat in the gun cabinet until yesterday. I thought I would give it a go only to find it was locked up solid. Stripped it today and the buffer washer had totally disintegrated to powder. Gave the internals a good clean up, fitted a new buffer washer and piston ring, gave it a light lube and reassembled it with the original spring (using the tip mentioned above). Tried a few different pellets but best by far power wise were the Defiant Vintage 14.5gr. Pushing them out a very respectable 600fps. Shoots quite nicely and I’m very happy with it

  13. #13
    Join Date
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    Quote Originally Posted by ken69 View Post
    I bought a virtually unused Airsporter S many years ago and it sat in the gun cabinet until yesterday. I thought I would give it a go only to find it was locked up solid. Stripped it today and the buffer washer had totally disintegrated to powder. Gave the internals a good clean up, fitted a new buffer washer and piston ring, gave it a light lube and reassembled it with the original spring (using the tip mentioned above). Tried a few different pellets but best by far power wise were the Defiant Vintage 14.5gr. Pushing them out a very respectable 600fps. Shoots quite nicely and I’m very happy with it
    I’ll try the Defiant Vintage next time.

  14. #14
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    Quote Originally Posted by Steve Zodiac View Post
    I’ll try the Defiant Vintage next time.
    Had a few shots this morning , interesting results at about 20 metres with open sights , Mercury S .22

    Pellets used .

    Marksman, Superdomes, Defiants, original wasps , modern wasps ..

    Accuracy results , best to worse .

    1, Original Wasps
    2, Modern Wasps,
    3, Marksman
    4, Defiants
    5, Superdomes.

    Tightest groups were the Eley and Modern wasps.

  15. #15
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    Quote Originally Posted by Steve Zodiac View Post
    Had a few shots this morning , interesting results at about 20 metres with open sights , Mercury S .22

    Pellets used .

    Marksman, Superdomes, Defiants, original wasps , modern wasps ..

    Accuracy results , best to worse .

    1, Original Wasps
    2, Modern Wasps,
    3, Marksman
    4, Defiants
    5, Superdomes.

    Tightest groups were the Eley and Modern wasps.
    I wish I could find a tin of original Wasps at a price that wouldn’t bankrupt me

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