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Thread: How to get a scope to focus at 10 metres.

  1. #1
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    How to get a scope to focus at 10 metres.

    We are currently having some fun shooting sporting air rifles with scopes at various targets in our club, but our indoor distance is fixed at 10 meters.

    Not all of the scopes that we have "dug-out" are AO or will focus down to 10 meters but they are good scopes that work well at longer ranges and if we can adjust them to give a sharp focus at this shorter range it would enable us to make good use of the ones we already own.

    We have been told by a few "passers-bye" that it would be possible to adjust the front lens on our non- AO scopes to convert the focus from the factory set distance ( 30 yards or so?) down to 10 meres.

    I notice that the front lens on our scopes do have a screw thread ahead of the front lens, so maybe this allows the lens to be moved in or out to adjust the focus down to 10 metres? I also notice that the scopes are nitrogen filled and suspect that "tinkering" with this lens could release the gas?

    If anyone has any succesful experience of making adjustments like this to a rifle scope and can advise us how to do it we would be very pleased to hear from you!
    Rossendale Model Target Club every Tuesday and Thursday evening 7 - 10pm.

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    Do none of them have adjustable diopter settings on the eyepiece?

  4. #4
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    If your going to be screwing the front lens in or out (I can never remember which was it is ) always pad and protect the front lens. I once saw an expensive Leupold damaged when the owner slipped with the tool (the tool) and scratched the lens.

    ATB
    Ian.

  5. #5
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    I looked into this recently. I do not have the search results but fairly sure it was wind the front element out a little, but as you say this might disturb the seal and let the gas escape. There was a thread on here recently by someone asking for companies that can re-charge a scope....because he had tried to alter the front element

    Turned out my scope (Hawke HD Sport) did not have an adjustable ring at the front....so I bought a Nikko Sterling 4x40 AO from our site sponsor for a very good price.

    I wonder if applying (carefully) more of the heavy grease (normally found in the threads of a scope/binoculars) would help minimise the risk of loss of the gas (presume it is low pressure)?
    Last edited by Aimstraight; 15-06-2018 at 10:26 AM.
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  6. #6
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    Quote Originally Posted by I. J. View Post
    If your going to be screwing the front lens in or out (I can never remember which was it is ) always pad and protect the front lens. I once saw an expensive Leupold damaged when the owner slipped with the tool (the tool) and scratched the lens.

    ATB
    Ian.
    I bought a skylight filter to protect the lens on a new camera. Within days I managed to mark the bloom/coating on the filter - the spring loaded lenscap slipped from my fingers and struck the filter - how unlucky is that! Just as well it was the filter not the lens
    Treat Others As You Would Wish To Be Treated.

  7. #7
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    Quote Originally Posted by I. J. View Post
    Listen to the 'passers-bye'.
    Was it you?
    Rossendale Model Target Club every Tuesday and Thursday evening 7 - 10pm.

  8. #8
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    Quote Originally Posted by Aimstraight View Post
    I looked into this recently. I do not have the search results but fairly sure it was wind the front element out a little, but as you say this might disturb the seal and let the gas escape. There was a thread on here recently by someone asking for companies that can re-charge a scope....because he had tried to alter the front element

    Turned out my scope (Hawke HD Sport) did not have an adjustable ring at the front....so I bought a Nikko Sterling 4x40 AO from our site sponsor for a very good price.

    I wonder if applying (carefully) more of the heavy grease (normally found in the threads of a scope/binoculars) would help minimise the risk of loss of the gas (presume it is low pressure)?
    I will make a suitable device to fit into the two small horizontally opposed slots in the front lens holder and if it will unwind OK I will move the lens forwards a little and see if this works.

    Some low tack masking tape should help protect the lens but I will put a concave curve into the device to help keep it away from the lens surface.

    Your idea about adding a little grease to the threads sound good too!
    Rossendale Model Target Club every Tuesday and Thursday evening 7 - 10pm.

  9. #9
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    What you are attempting to do is re-paralaxing, not all scopes are suitable for this so it would depend on the make/model. Fabricating a tool to fit into the slots that you see on the lens carrier is one way and if the lens carrier is stiff then a small amount of warmth or heat may ease the situation but you must be prepared to accept that the scope could become trashed if the tool slips or you otherwise force the situation.

    Ideally, scopes with a decorative trim ring at the end are the easiest. Remove this with a couple of Mini Boa's, if it comes clean off the lens carrier then just wind the carrier out about 1/4 of a turn then check focus/parallax for your desired range and re-adjust as/if required. When all is good re fit the trim ring without upsetting the carrier, this bit can be tricky!

    If the trim ring brings with it the carrier then only turn the whole assembly 1/4 turn and check as above. Once you have focus/parallax you have to lock the trim ring and carrier with tape of the black insulation variety.

    Hope that makes sense.

    Edit: The nitrogen, if that is what the scope was constructed using, is not under any pressure as such. It is used to purge the internals of air which itself contains moisture, the nitrogen is "dry". Moving the carrier should not allow the nitrogen out in the pressurised gas sense, removing the carrier totally and complete with lens will, simply moving the carrier forwards should not.
    Last edited by Portzy; 15-06-2018 at 04:46 PM.

  10. #10
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    Well said Portzy and I agree with everything you have put.

    Small thing to think about for those still concerned about the Nitrogen filling: Does you scope have an adjustable eye bell? (nearly all do). Does your scope have a zoom? Just how good at retaining Nitrogen are those sliding seals after years of movement? Unless you are taking the thing apart do not worry about letting the magical Nitrogen out.
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  11. #11
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    Explanation from Portzy helps.

    The link below might too:

    https://youtu.be/T97GCZqbZio
    Treat Others As You Would Wish To Be Treated.

  12. #12
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    Quote Originally Posted by zooma View Post
    Was it you?
    No.

    With a name like ZOOMA I thought you would have been an expert with scopes.

  13. #13
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    In the past I have used a pair of straight engineers calipers to unwind lens carriers. I used the kind that have a threaded rod between the legs.
    Donald

  14. #14
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    Quote Originally Posted by thisisdonald View Post
    In the past I have used a pair of straight engineers calipers to unwind lens carriers. I used the kind that have a threaded rod between the legs.
    I may try that - it would save making a special tool.
    Rossendale Model Target Club every Tuesday and Thursday evening 7 - 10pm.

  15. #15
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    10 MT focus

    Hi Bob

    I shot ten metre running boar (Running rat) quite seriously many years back, Now PC incorrect, and now just moving target, we had the same problem getting scopes generally set for 100 mts correct at 10 mts.

    Don't mess about trying to adjust the lens its a real hassle, what we did was go to a local lens maker/optician, you need a +0.1 dioptre lens added to the front, the tolerance on plain lenses is 0.1 of a dioptre, which is what you need, if you have a friendly one he will sort and test his plain lenses until he finds one on 0.1.
    Get it ground to the correct diameter, then pop out the front ring put an "o" ring either side of the lens and pop the ring back. Voile, corrected to ten metres, and easy to take out to return scope to standard.

    Have Fun
    Robin
    Steyr LP2 Short - Walther CP2 - Walther LPM1 - Walther LP53 - Feinwerkbau 65 - FAS 604 - Walther LGV - Walther LGR - Walther LG400 Alutec - Walther KK300 Alutec - Swing 7.62 mm in Walther stock. - Keppeler 6 mmBR with Walther grip and wood!

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