New FT Ballistics App - Any Feedback on it's Wind Performance?

Discussion in 'Hunter (HFT) & Field Target (FT)' started by pirellip, Aug 22, 2014.

  1. pirellip

    pirellip Member

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    Folks,

    I've been using a new ballistics program developed specifically for FT shooting. I really like it, but being from Canada, where there's at most 100 FT shooters, I can admit that my exposure to FT is limited, especially in the wind.

    It's called PP-Calc
    https://play.google.com/store/apps/details?id=com.harryslad.rwpoi&hl=en

    I have met the author, and he's a very technical guy and what I like about this program is that it segments the calculations into 3 separate BCs, from real world data entered at 4 distances (nearest target, zero, farthest target, and 1/2 between zero and farthest).

    Fundamentally it's (similar to a curve fitting software, but grounded in Newtonian physics.

    Has anyone else been using this, and if so, do you find it accurate with the wind drift predictions? Unfortunately our shooting venue doesn't get much exposure to the wind.

    Thanks!
     
  2. Martz

    Martz Member

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  3. pirellip

    pirellip Member

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    It's Fundamentally different than Chairgun

    Hi Martian,

    The developer is Héctor Medina, who's currently living in the US.

    Whereas Chairgun is purely theoretical and assumes a constant BC, this program uses the data you input from the 3 distances to break the trajectory down into 3 segments, each with their own BC.

    However in the real world, BC is a dynamic value, and is always changing as the pellet travels through the air.

    Also, this program takes into account shimming of your scope, which Chairgun cannot.

    The theory of this program is very intriguing, I've found it to match my real world clicks well, but can't really see if it matches the wind doping side of things!
     
  4. Adam

    Adam Active Member

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    From the URL you posted in the OP:

    /store/apps/details?id=com.harryslad.rwpoi&hl=en

    Harry's Lad is the forum nickname of the developer of Chairgun and Hawke BRC.

    Eh? :confused:

    Shimming of your scope is irrelevant for trajectory calculations. Shimming affects the angle of the scope tube, to compensate for lack of adjustment range or optical centring. All that's relevant to Chairgun is the zero range and the height of the sight line above the bore. The sight line being the line through the centre of the reticle which goes through the axis of the erector tube, not the axis of the scope tube.
     
    Last edited: Aug 22, 2014
  5. fireblade

    fireblade Team AirArms

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    This reads like an add, and as the app needs to be purchased, this post should be in the for sale section.
    jmo oc.

    Conor!!!!!!! Go get him!! :)
     
  6. pirellip

    pirellip Member

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    Hi Adam,

    Yes you are correct that the scope has no effect on the pellet's path through the air! I had just recently learned this, but didn't recall it - never was all the proficient in school! :cool:

    As I'm learning about the mechanics of how a scope works, and the relationship between your sight picture and the pellet trajectory, I'm correcting MANY of my previous misconceptions - eventually I'll remember them all!

    In Canada, we have a 'blended' set of rules that we've developed from taking bits and pieces from other countries. With respect to Hit Zone sizes, we follow this approach:
    1/4" - up to 15 yards
    3/8" - up to 20 yards
    1/2" - up to 25 yards
    3/4" - up to 35 yards
    1.0" - up to 45 yards
    1.25" - up to 50 yards
    1.50+" -up to 55 yards

    However many of us shoot under the WFTF format, so our scope setup is pretty important, as we still try to hit the same stuff at sub 12fpe as others are shooting at with sub 20fpe.

    But I digress! I'm off the NZ zon Monday for the big match, and have been warned about 'Windy Wellington' but just haven't been able to practice in the wind - so I'm hoping that I can learn *something* about where my pellet is going to land by studying ballistics software!

    Hoping I could get some feedback on this software's ability to do this since I can't test it's predictions out myself.

    Yes, I am aware of the Chairgun Mobile App, but for some reason it doesn't display any data past 38 yards on my phone (and I've tried MANY things to solve this):eek:o
     
  7. pirellip

    pirellip Member

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    I was concerned that some may read this post as an 'add' and tried to word it in such a manner to avoid this!

    I have no 'stake' in this program, besides having met the author a handful of times at shooting events in the US over the past few years.

    Yes the app costs $5USD, but besides Chairgun Mobile, I can't seem to find anything else that is Airgun ballistics specific that runs on my Android.

    I will say that after doing some searching in to what Héctor has posted on other airgun forums (the US FT form and the Diana forum) he seems to always be willing to share his knowledge and opinions in a very detailed manner freely!

    I won't get in to the philosophy of 'paid vs free'; it's not the intent of my post. Advertising this app also isn't the intent of this post!
     
  8. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Have you tried having a play on the FT Wind simulation game Tom?

    http://www.competitionshooter.co.uk/windeeze

    You might need to refresh the page once or twice, it seems to be running really slowly today for some reason.

    See you out in NZ - it's looking a bit windy at the moment - forecast for today was 29mph in Lower Hutt :eek:
    Just remember an old Yorkshire tip for shooting in the wind - "If in doubt, girret nowt" :D
     
  9. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Just to clear up a couple of points you've raised.. Chairgun doesn't assume a constant BC, it uses a "DragFunction" table and has 11 bandings for the drag when the pellet is travelling below 810 fps.

    So essentially what it does is alter the effect of the BC 11 times over the course of the trajectory for a sub 12fpe projectile.

    These drag tables aren't purely theoretical either - they're based on thousands and thousands of controlled real world ballistics experiments over the past couple hundred years.

    Shimming of the scope?.. Chairgun asks for a parameter which is the Line of sight height above the bore. If you measure this correctly, that measurement takes into account Shimming, Barrel Droop and Muzzle flip as well as some other factors too.

    I have more than a sneaking suspicion that P-Calc will use the same publicly available ballistics calculations as Chairgun at it's core. It sounds like P-Calc has some alternative methods of measuring the input values required for this calculation which is interesting.

    It is true to say that the Line of sight above bore will change when you change your elevation turret and this is something that Chairgun doesn't take into account, which is sounds like P-Calc does.

    However.. the difference to the trajectory that this makes is so slight that you'd be extremely unlikely to notice it in the real world.

    Hey - if it works for you great. Really it all depends on what you hope to get from the app.
    (btw - the wind game uses the same publicly available ballistics code as Chairgun and very probably P-Calc too, although it assumes you're shooting at the Standard Atmosphere, because I couldn't be bothered to add input fields for environmental conditions :) )
     
  10. pirellip

    pirellip Member

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    THANKS BRIAN - I've leaned quite a bit from this post! I've been playing with your FT Wind Simulation - I'm getting a handle on it, hopefully I can decipher what Xmph 'feels like' in the real world - perhaps I'll drive around a country road with my head out the window :rolleyes:

    Turns out my current mobile phone can't be carrier unlocked (it's hard locked) so I just purchased a new mobile that is unlocked so I am connected while away - hopefully Chairgun Mobile will work properly on it!

    See you next week!
     
  11. rich

    rich Active Member

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    Forget about sticking your head out of the window. Get your whole body out of the car. Turn around on the spot until the wind is on your back and the noise is the same in both ears. Provided you are not wearing a hat or deaf in one ear, you are now roughly facing the same way as the wind is headed. This is how to assess direction.

    Now walk forwards at a brisk pace away from the wind. Is the wind still on your back? If it is, then the wind speed is greater than your walking pace, which for most men is around 4 mph. If you can't now feel the wind on your back then you are going faster than the wind.

    A 4mph broadside wind will make your 177 pellet at 12fpe drift more than two inches at 50 yards.

    Hope this helps. Wind assessment is part physics and maths, and part experience, and part luck as well. The first you can learn without even touching a gun, the second you can now get a handle on with Brian's excellent program, and the third, well, you're on your own with that. :)
     
  12. pirellip

    pirellip Member

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    Thanks Rich!

    I really appreciate the advice!
     
  13. pirellip

    pirellip Member

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    Chairgun Mobile has been updated - and it now fully works!

    I just wanted to say Thanks to all the wind tips I received from people at the NZ Worlds!

    I discovered that the 'theory' provided by Chairgun/PPCalc and Brian's simulator was very helpful, but nowhere near as much as the discussions/tips/advice I received from the 'boots on the ground' people there :D
     
  14. MattJP

    MattJP New Member

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    Care to share those tips?

    I'm glad you had a good experience at the Worlds. Nice job in the competition!

    Best,
    Matt
     
  15. pirellip

    pirellip Member

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    It's tough to type them down on paper, as I learned by receiving tips during shooting.

    Fundamentally though, you can't just 'follow your windicator' as is often the approach for shooting powder burners.

    You have to read what's going on further down range. I believe that the last 1/3rd of the distance is critical, as the pellet has slowed quite a bit and thus spends more time in this section of air.

    Use the target string (something I NEVER did before) it'll tell you a bit.

    Use other people's misses as a hint.
    Use the lane's natural surroundings to see what's going on.

    For example: one lane in NZ (I think it was White 20?) it was a long 45m+ shot over a pond, and there were a corpse of trees about 30m in front of me, off to the right. I held up the target string, but it didn't 'bow' in any significant way (that I could tell at least, but I'm a newbie) and my windicator was showing a right-to-left wind. Okay I thought, I'll aim to the right. Then I noticed that the target string, while sitting on top of the water was making an 'S' curve - the wind was blowing it to the left near me, but blowing it to the RIGHT closer to the target. I thought "what the heck, I'll aim to the LEFT even though the wind AT me is blowing that way!" and the target fell!

    I quickly came to the conclusion that I need a LOT more practice in the wind... but the ONLY club that is within a 4 hour dive has next to NO wind. On a 'gusty' day, it's 5mph... I NEED to find a farm to shoot at!

    Hope this helps!
     
  16. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    That's what I like about FT. That feeling you get when you figure out what the winds doing and knock that long target over. (especially with a springer)
     

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