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Thread: Guess the inaccuracy issue BSA Mercury

  1. #31
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    Quote Originally Posted by Captain Bongo View Post
    It's a trick question. There is no inaccuracy issue. 1 inch at 10 yards is pretty good for a Mercury.
    Thats a bit strange tbh,I used to hit spent 12 bore cartridges using open sights
    over and over down the fields until I couldn't really see it anymore ,so quite a bit further than 10 yards lol.

  2. #32
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    Quote Originally Posted by jjjohn View Post
    Use 5.6 instead of 5.5 pellets.

    oops though it was .22 ,my bad
    Wrong calibre but right track I think, BSA (and Webley) always had slightly different bore sizes to the european makers, try some ely wasp or similar pellets and things might improve
    Do nothing, achieve nothing

  3. #33
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    Quote Originally Posted by pbranthwaite View Post
    Wrong calibre but right track I think, BSA (and Webley) always had slightly different bore sizes to the european makers, try some ely wasp or similar pellets and things might improve
    My .177 meteors which are of the same period, perform very well with JSBs, so modern pellets are not the issue.
    However, modern Superdomes, which the OP used, are not always great in many guns.
    Too many airguns!

  4. #34
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    Quote Originally Posted by look no hands View Post
    Mine don't, so what did you do wrong

    Pete
    Lots of shims under the nut and bolt head to get enough compression on the forks.
    Too many airguns!

  5. #35
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    Mine has three shims under the bolt head. Some parts diagrams show four. When I was to first work on mine, when ordering the parts I ordered another shim but the gun didn't seem to want to accept that extra one so I re-built with the original three. When cocking and re-closing the barrel I see that the entire nut and bolt rotate.. It's one of the areas I want to address on the next fettle. I have been told by someone that the number of shims used isn't a definite number and that the factory used varying numbers depending on the fit and tolerances between different guns? Anyone else come across this? I've also wondered whether the tension from the detent latch and spring have anything to do with this?
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  6. #36
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    Quote Originally Posted by TonyL View Post
    I've also wondered whether the tension from the detent latch and spring have anything to do with this?
    That is perhaps the biggest issue with the lockup system on the BSA breakbarrels, the chisel tends to bind on the pin.
    On some guns it is necessary to increase lockup tension with a few washers under the locking spring, and this of course increases the problem.
    Too many airguns!

  7. #37
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    Mmmmm........thank you, evert.. Scratches head..
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  8. #38
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    Interesting comments about the barrel bolts for BSA's of this era. The 'simple' bolt solution has often been the way to compensate for the forks opening up but if the bolt rotates then at first it sounds like its a candidate for having a lock screw fitted to prevent it happening. However if it is locked would the lack of rotation cause excess wear on on it in one spot by the barrel latch, maybe increasing the chance of vertical allignment / consistency issues. (hence loosness & needing to pack the latch spring?) Do you think that it might be better to allow the pin freedom to rotate instead or just watch out for wear to the bolt & replace as needed?

    Reverse choke on BSA barrels is a new one on me.....how the heck does that happen?

  9. #39
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    Quote Originally Posted by trajectory View Post

    Reverse choke on BSA barrels is a new one on me.....how the heck does that happen?
    Should imagine it's where the barrel is pressed into the breech block by a company that doesn't care much about what they do.
    Good deals with these members

  10. #40
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    Quote Originally Posted by eyebull View Post
    Should imagine it's where the barrel is pressed into the breech block by a company that doesn't care much about what they do.
    .....goodness knows.

  11. #41
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    I am now of the opinion that this is not a 'guess the answer' thread but the search for an answer. In other words, the OP does not have a clue what is happening and is hoping to get inspiration from here.
    I was hoping that the OP had found the answer and was going to tell us in order to broaden our experience / knowledge.

    So, come on .... what's the answer?

    Cheers, Phil

  12. #42
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    Quote Originally Posted by eyebull View Post
    Should imagine it's where the barrel is pressed into the breech block by a company that doesn't care much about what they do.
    The barrel isnt pressed into the breechblock on any BSA springer.

  13. #43
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    Quote Originally Posted by greenwayjames View Post
    The barrel isnt pressed into the breechblock on any BSA springer.
    It is brazed, and that can cause distortions too.
    Too many airguns!

  14. #44
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    Nothing to do with the rifle, everything to do with the scope and mounts.
    Tac drives at 10m with its iron sights.

    Or you thought you had bought a .177 and its a .22 Stop feeding it the wrong calibre.

  15. #45
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    Quote Originally Posted by Hsing-ee View Post
    Got a nearly new BSA Mercury Mk IV .177 and it groups like 1" at 10 yards with RWS Superdomes. The breech bolt is tensioned correctly.
    The trigger isn't great, but really this is springer pistol-level accuracy.

    Before I do stuff to it, do you think it is

    a. A dirty barrel.
    b. A dislike of RWS Superdomes.
    c. A scope issue.
    d. A barrel crown issue.
    e. Poor technique by me.
    If you have only tried one pellet in it, what do you expect? Surely you will test other pellets before you do stuff to it ?

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