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A Chairgun question re penetration

Discussion in 'Anything Airgun Related' started by Dag, May 12, 2014.

  1. Dag

    Dag Pro Poster

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    In the ballistics table displayed by Chairgun there is a column showing penetration in inches.
    The figures on the graph I am looking at ,which is for a 10.60ftlb rifle with range 0-60yds, are 3.47in at 0yds through to 2.48in at 60yds.
    Just out of interest I started looking at the Help info to see how this was measured and into what material. All I can find is the following:
    Penetration
    Penetration using the Poncelet/Steve_NC expression
    I guess it's not too important but I wouldn't mind knowing what this means in case someone else asks.
    Can anyone help?
    Dag :confused:
    ps I have Googled it but it either sends me back to Chairgun's Help pages where I started or numerous pages re people called Steve or Poncelet!
    pps I have also left a query with Hawke so may get some info from them........but can you beat them to an answer?
     
    Last edited: May 12, 2014
  2. abye

    abye Engaging Member

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  3. Dag

    Dag Pro Poster

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    Thanks Abye, at first glance it covers the maths but I probably should have said I was looking for the more practical interpretation of what material is used, which pellets etc and then how that is used to get the penetration figures. What you have provided is, no doubt, exactly the equation they use but I do wonder what tests they carry out to get the raw data.
    atb
    Dag
     
  4. Dag

    Dag Pro Poster

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    I contacted Deben/Hawke and received this reply:

    Hi,
    ChairGun4's method is based on Steve Woodward's insigthful analysis of the original Poncelet equations.
    Steve's original post can be found at: http://www.network54.com/Forum/7953...et+Bullet+Penetration+Math+applied+to+Airguns

    In practical terms:
    Permanent_Wound_Channel_Volume(cu.in. of flesh) = Pellet_Weight(grain) x Impact_Velocity(fps) / 67500 .
    There are some caveats on velocity margins etc., but air pellets basically meet those.
    or, more simply (at airgun energies and velocities) :
    Penetration_Depth (inches of flesh) = Pellet_weight(grain)/Area(in²) x V(fps) / 67500

    The Penetration curves in ChairGun4 should really only be used for comparison purposes - rather than as absolute values - since we have no knowledge of other salient variables. i.e., density and homogeneity of the target medium, relative shear strength of the boundary layer (skin/fur/feather).

    Regards,
    Deben Group Industries Ltd

    I don't pretend to understand all that the maths implies but there is a summary from them, which I have highlighted above, referring to the relevance to air weapons which may, or may not, be of interest.
    At least I now know the formula nd basis of the penetration figures given against varying velocities and pellet weights in Chairgun
     
    Last edited: May 13, 2014
  5. tintin

    tintin Engaging Member

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    Thanks for taking the time to investigate this.
    Knowledge is always good. However it does depend on density and any other obstructions - basically this is not a real world test, bones etc tend to get in the way when hunting, but for someone with a technical mind .............
     
  6. Dag

    Dag Pro Poster

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    Absolutely, and as stated in the article :
    Penetration curves in ChairGun4 should really only be used for comparison purposes - rather than as absolute values - since we have no knowledge of other salient variables. i.e., density and homogeneity of the target medium

    Dag
     
  7. Georgie

    Georgie Newbie

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    I too am perplexed by the "Penetration" data in CHAIRGUN
    . I had assumed that there was some sort of notional field-sport ballistic density comparable with (Say) rabbit or other common target animal. Taken at face value, the numbers would suggest a sub 12fp gun would fire straight through just about anything that moved within a 50 yard radius. Even as a comparison number I can't easily see how it can be used. Hunting haggis maybe?
     
  8. Dag

    Dag Pro Poster

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    "The Penetration curves in ChairGun4 should really only be used for comparison purposes - rather than as absolute values - since we have no knowledge of other salient variables. i.e., density and homogeneity of the target medium, relative shear strength of the boundary layer (skin/fur/feather)."

    My understanding of Deben's answer is to not get too hung up on the penetration values and to consider them as relative values rather than absolute ones as they themselves haven't a clue as to the material used for establishing those value. It's one of those columns of information provided by Chairgun that I choose to hide to give more space for displaying the trajectory curves.
    Dag :)
     
  9. Funky Diver

    Funky Diver Donator

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    I would imagine, and imagining is what I would do in this scenario, that it'd be akin to shooting into ballistic gel as a substitute for flesh.

    Making some form of equation to calculate these things would require a constant and shooting into real flesh would give too many variables to be able to calculate anything.

    But this is obviously not going to give the same physical make up of any particular flesh being that it's consistent by design. As such it would give rise to some form of formula made by the Steve dude (without looking at the links you kind folks gave - but I intend to once I get some time on my hands later :D). What it will give you though is something to work on if you hunt the indiginous Balistico Gellohog roaming wild in southern Dakota :D
     
  10. 177

    177 Donator

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    I read a piece recently where the consistency of ballistic gel was coming into question.

    It went something along the lines of variables in preparing it, environmental influences (ambient temperature and humidity) and other whatnots.

    Having a standard to measure by is all well and good.

    My take: hit what you aim at. Watch if fall over dead. Rinse and repeat.
     
  11. GPConway

    GPConway Busy Member

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    To be fair, the penetration expression is stated to be derived from Poncelet's equations in which a target density of 1 gram/cm³ and shear strength of ~600 Lbf/in² are assumed. i.e., as human/porcine muscle fibre. That would be because Poncelet's equations were derived as a method of assessing human battlefield lethality and (probably) tested extensively on pigs as analogues.:)

    These density and shear strength values are also repeated in Steve Woodward's original post.

    George
     

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