Chairgun

Discussion in 'General Airgun Chat' started by kev53, Dec 19, 2013.

  1. kev53

    kev53 Member

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    Can someone answer a question about chairgun, my scope height is two inches, I,m zeroed at 35yards so when I put this in to chairgun for 10yds it's saying I should be aiming 1.3 above but using this setting I miss the target,if I shoot at 0.5 I hit the target can anyone explain why.
     
  2. Shaun

    Shaun Active Member

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    Hi Kev,

    I've put in some basic info (zero at 35y, scope height 2", 0.177, 785fps) and I get 0.58" high.

    What is the you near zero?

    Shaun
     
  3. Conor

    Conor Never been banned from sales Staff Member

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    I'm pretty sure 35yrds isn't your zero if your centre of scope to centre of barrel is 2". It should be 30yrd zero.
    You should aim 0.67" above target centre for a hit at 10yrds.

    Your inputting something incorrectly. Even with a 35yrd zero your aim point is 0.6" above centre of target.

    Your better doing them on paper using a tape measure to be absolutely sure. Its best way.
     
  4. Strokebloke

    Strokebloke Mk3 Fanatic

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    Possibly because you have determined the height of the scope as 2", from the centre of the barrel to the centre of the scope at the position of the scope. The height of the scope is the line of sight from the line of fire [or pellet flight] at the muzzle. Almost certainly significantly less than 2". :)
    Simple trig will determine a much more accurate assessment of the height of the scope above the line of fire, at the muzzle.

    ATB
     
  5. kev53

    kev53 Member

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    I zeroed in to 15yds as this is the same aim point as 35yds.
     
  6. Shaun

    Shaun Active Member

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    Simple trig? Come on a Jack you'll do me out of a job!
     
  7. Bernie

    Bernie Love to Bracket

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    This is how i sorted out my Ranges on Chairgun or got close :-
    Go to a range and zero your gun to a zero your happy at, then put out a piece of card or paper at preferable range (50 yards) is what i did mine at, put your crosshairs at the top of the paper keeping the crosshairs in the same place and steady, and shoot a group of say 10 pellets, then take a measure in inches from the top of the paper to the centre of the group.
    Take a note of this measurement.
    Now go onto Chairgun.
    Click Tools at the top
    Click Calculator
    Click BC from POI
    Then fill in the relative boxes - Scope Height
    Zero Range
    POI = Is the measurement of drop in inches that youve noted
    Target Range = Is the range (50 yards) of the piece of paper you put out.

    Hope this helps
    Better still, just go to the range and range out all your shots on card or paper rather than Chairgun.
     
  8. kev53

    kev53 Member

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    Thanks to all,I'll try Bernie's idea and go from there.
     
  9. Scottish Guy

    Scottish Guy Member

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    You have your scope hight wrong as strokebloke told you:eek:o
     
  10. kev53

    kev53 Member

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    I realised what I have done,I had the mag on chairgun different to the mag I zeroed in on.
     
  11. Dafted

    Dafted New Member

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    Nice one Kev all sorted now :),,,,
     
  12. Conor

    Conor Never been banned from sales Staff Member

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    1.3" is still 1.3" no matter what magnification you set your scope at??:confused:
     
  13. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    My guess is, that he means 1.3 mildots not 1.3 inches.

    In that case my best guess at the problem would be that the mag on your scope isn't at it's true mildot setting.

    btw, to get accurate results (although it won't matter in this case) you do need to enter the correct line of sight above muzzle value (it's NOT scope height). The best and most accurate way to do that is the tin foil method.

    @Jack - Simple trig unfortunately will not work because there are some unknowns that you erm.. don't know :)
     
  14. blacklab

    blacklab Member

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    barrel to scope

    its critical to get center of barrel to center of optic right
     
  15. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    That's the mistake most people make with the calculation.

    Centre of optic to centre of barrel is NOT the measurement required for the ballistics calculation used by Chairgun and pretty much every other ballistics calculation apps available.

    The measurement required is the distance between line of sight and muzzle, directly above the muzzle.

    If you're measuring the height of the scope above the barrel, you're measuring the wrong thing. To be fair it's not a million miles off, but it isn't the right value to use and will give noticeable trajectory differences to longer range.

    For this question though, the difference won't be noticeable because we're only talking about 10 yards.

    Here's a little diagram to illustrate what I mean.. scope-height-measurement.pdf
     
    Last edited: Dec 20, 2013
  16. Adam

    Adam Active Member

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    Laser boresighter, and "similar triangles". ;)
     
  17. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    hmm.. yeah that might work :D

    Tin Foil is cheaper than a Laser boresighter though (and more useful)
     
  18. Bernie

    Bernie Love to Bracket

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    Blimey Brian, you've lost me on this one, surely this way it would mean putting the gun Iin some sort of clamp to get a correct measurement. How does the tinfoil method work.
     
  19. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Basically you just put a card right on the end of the barrel and measure the distance between what you were aiming at on the card and the hole the pellet makes in the card.

    The difficulty with that is that your scope won't be able to focus down that low (the end of your barrel), so to increase the depth of field of your scope so you can actually see a cross on a card that's right on the end of your barrel you need to rubber band a bit of tin foil over the end of your scope and punch a small hole in the centre.. you should then be able to focus on the card.
     
  20. Bernie

    Bernie Love to Bracket

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    So this measurement then is the scope height in inches in the top right in chair gun.
     

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