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Thread: ballistic calculators for long range airgun shooting

  1. #1
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    May 2013
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    Bearsden
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    ballistic calculators for long range airgun shooting

    I am sure long range air gunners can help me with this. I used a number of different ballistic calculators and found that nearly all of them for the same ammo and conditions give different data, confused which one to trust. And after printing few tables I did some test shooting and result I got do not match with any BC, very confusing.

    Do you guys use BC for drop calculations or finding out hold over / under by shooting at different distances and making your own tables?

  2. #2
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    Apr 2012
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    Quote Originally Posted by svds View Post
    I am sure long range air gunners can help me with this. I used a number of different ballistic calculators and found that nearly all of them for the same ammo and conditions give different data, confused which one to trust. And after printing few tables I did some test shooting and result I got do not match with any BC, very confusing.

    Do you guys use BC for drop calculations or finding out hold over / under by shooting at different distances and making your own tables?
    ChairGun is supposed to be amazing. I witnessed a gent using it the other night and he was shooting really well.

    Worth a look, and is available on smartphones (ios/android).

    Free as well from memory..

  3. #3
    Join Date
    Apr 2014
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    SLOUGH
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    I have found chairgun to be a very useful tool. It is indeed free !
    After trying a few distances with the same zero on my scope, as was in chair-gun - the POI calculation seemed pretty spot on (couldn't go over 25m though)

  4. #4
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    I've tried chairgun on the PC and it worked fairly well, but Im using Strelok now which also matches reality pretty well and has better interface for small android devices.

  5. #5
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    Sep 2009
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    using any method for calculating BC will still only be a rough guide at best!! as the same ammo from a different barrel will give a different result.The calculations of the manufacturers as printed in Chairgun are an average only,and never exact.These will however get you as near as you really need to be in the real world.Chairgun will get you 95% of the way and you simply fine tune for your own shooting, by trial and error.
    [URL=http://www.ukchineseairgunforum.org.uk/index.php[/URL]

  6. #6
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    May 2014
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    When refined by using muzzle velocity data it gets pretty close - definitely a useful learning tool if nothing else.

  7. #7
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    May 2013
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    Bearsden
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    BC

    Thank you guys for explaining, going to have few shooting sessions soon to test which BC gives closest data for my guns, but pretty sure that walrus1# is right - "BC will still only be a rough guide at best", will see.

  8. #8
    Join Date
    Dec 2013
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    Ware
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    Define long distance?

    For the most accurate chairgun setup...

    Weigh some pellets, collect a batch of the same weight to use for your crono testing.

    Chrono your gun at the muzzle and again at a set distance with your weighed pellets.

    These 2 will be able to create an accurate BC for your pellet and the correct muzzle velocity for your gun.

    Then an accurate zero is needed, like spot on, gun clamp, bench and indoor range till you can pellet on pellet at your zero distance.

    Then you need the correct scope to barrel measurement, most people do this wrong by just measuring between the centreline of the barrel and the centreline of the scope, that IS NOT how it should be done, it should be measured at the end of the barrel and be the distance between where the crosshairs project on an item at the end of the barrel and the centre of the barrel (note: 'barrel' not moderator), full instructions are in the manual...

    Then you measure and input the distance between the end of the barrel and the reticle (centre turret) and input that, then you have chairgun set up as close as possible...

    Then the wind blows, the temperature changes, your pellet weight isn't spot on or your rifle is having a bad day and it all goes to shit anyway lol
    BSA R10 MKII VC .177
    MTC Viper 10x44

  9. #9
    Join Date
    Jun 2019
    Location
    Lima, PERU
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    Strelok Pro has been working really well for me on my mobile phone.

    It has a huge selection of reticles to choose from.
    It allows you to define and save a bunch of different configurations ("rifles").
    It has a pellet data base, but you can enter variable pellet BCs for different speeds, and even a full custom drag model.

    Matthias

  10. #10
    Join Date
    Sep 2021
    Location
    Birmingham
    Posts
    39
    Chairgun can do all sorts of things. Another intended just for ranging work is Mero. it's available for all platforms and pretty easy to use. One obvious feature that may confuse is 2 scope magnifications. One is actual scope magnification where the calibration of the reticule is correct - the other is for the magnification the shooter wants to use. That can be the same or different.

    Like always though the results need checking with real shooting.

    BC's. I have heard that Chairguns method is not that precise and 2 spaced crono's is a better way. It seems Pyramid Air has a calculator on it's web site for that method. This is something I have not personally tried.

    For BC's this page may be a good source. They use a radar unit that can actually track the pellets.
    https://hardairmagazine.com/ballistic-coefficients/

  11. #11
    Join Date
    May 2020
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    ECKINGTON PERSHORE
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    95
    Having seriously looked at Ballistic Coefficient and any benefit it can produce for air gun use, it appears there is no constant BC for any same brand pellet. Minute differences in weight can alter the BC as can velocity so what is the point of persisting with its use. Consider that velocity variation is common even in PCP's fitted with a regulator, a springer with its wider variation has less chance of consistency, add to that any weight or dimensional difference, BC has little chance of being a constant that has any worthwhile benefit.
    Having shot many different rifles over a 60 year association with them, I believe the only true way to set up and hit long range targets is with trial and error, perseverance aided by a little Strelok Pro on a still windless day recording the scope turret settings for future reference. I look at BC, weighing pellets, washing and resizing them, barrel harmonics, barrel cleaning etc and think what its all coming. If you believe all this is necessary then the days of loading your favourite pellet into your favourite rifle are numbered as you will need to check some computer app before proceeding.

  12. #12
    Join Date
    Feb 2015
    Location
    Llandudno
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    178
    I shoot five shots through the LMBR2 take the average fps (normally 4fps spread with weighed pellets in a HW100 .20) then shoot through through it at 35 yards and take the 5 shot average .
    Then use pyramid air calculator and feed results into IStrelok. Gives me a BC that works for dialling the swfa scope.
    Obviously all the other info IStrelok requires has to be accurate for everything to work .

  13. #13
    Join Date
    Mar 2012
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    Maidstone
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    Quote Originally Posted by 4end View Post
    Having seriously looked at Ballistic Coefficient and any benefit it can produce for air gun use, it appears there is no constant BC for any same brand pellet. Minute differences in weight can alter the BC as can velocity so what is the point of persisting with its use. Consider that velocity variation is common even in PCP's fitted with a regulator, a springer with its wider variation has less chance of consistency, add to that any weight or dimensional difference, BC has little chance of being a constant that has any worthwhile benefit.
    Having shot many different rifles over a 60 year association with them, I believe the only true way to set up and hit long range targets is with trial and error, perseverance aided by a little Strelok Pro on a still windless day recording the scope turret settings for future reference. I look at BC, weighing pellets, washing and resizing them, barrel harmonics, barrel cleaning etc and think what its all coming. If you believe all this is necessary then the days of loading your favourite pellet into your favourite rifle are numbered as you will need to check some computer app before proceeding.
    99% of the factors you are talking about produce minute changes in BC, which will have no effect on computed trajectories. Weight will only affect the sectional density. If your velocity variation is so high as to change the pellet BC, even with the wrong reference drag law, you have a lot more than BCs to worry about. Again, any dimensional differences will have to be pretty severe to make a real change, particularly after the pellet has been squeezed through a barrel.

    The biggest causes of changes in BC are experimental technique, not taking into account atmospheric conditions, and use of unsuitable reference drag laws.

    I am no lover of the BC system, particularly for long range shooting. For accuracy of predictions, the use of purpose drag laws is much more accurate but, unless you can produce them yourself, there are none available.

    But again, no-one is saying using a trajectory model will immediately put you on target, even a large gun's fire control cannot do that. It will put you in the right area to start the process of setting up your sights for long range, thus getting rid of a lot of effort and pellet waste, but the models need to be used correctly, which unfortunately is often not the case.

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