GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: JungleShooter on August 20, 2018, 08:03:06 PM
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I’ve been messing with ChairGun and trigonometry, but somehow the answer eludes me. A forum search has not brought up anything either. Can someone help me out?
For example:
I shoot upwards into a tree branch (7y high, 20y away from me), at an angle of 18 degrees up.
Say I use a JSB Domed .22, at 665fps MV, and 0.023BC (Thanks, Bob [rsterne] for your awesome work on BCs). I zeroed the gun for 35y.
Now, in case I miss my target up in the tree, where does my pellet end up?
When I enter the data into ChairGun4, I can find out my pellet's “Drop from LoD” [Line of Departure], also called “Drop from Boreline.” At 100y, my pellet dropped 57”, at 200y it dropped 355”, and then at 370y ChairGun decides it doesn’t want to show me any farther distances – so at 370y my pellet dropped from the LoD 3479”.
I can go through the same with the “POI vs. Range” ballistics table. At 100y, my POI is 34”, at 200y 296”, and at 370y it’s 3230”.
OK, fine, but it just doesn’t tell me at what distance my missed shot hits the ground (or the line of houses that are at some distance behind the tree I’m shooting at). :(
The other five ballistic calculators I’ve tried so far give me even less information.
Thanks for your help (btw, I’m not a physics or math crack, so... go easy!) ;-) ???
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Very interesting question. Not sure how you will get a precise answer though beyond trial and error. I would think a few hundred yards would be all a diabolo pellet could travel and 18 degrees is a bit low for maximum range so maybe 300 yards or so as a guess. I bet some of our more "ballistically accomplished" posters can give a more precise figure.
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You don't give pellet weight but a 16gr pellet across level ground while shooting from a standing position would take it to about 155 yards according to the ballistics trajectory calculator at shooterscalculator.com
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Yeah, the pellet is the regular JSB Domed (not the RS, Express, Heavy, etc.) = 15.89gr
I checked the Shooterscalculator.com (ShoC), and it does something that ChairGun (ChaG) doesn't do -- it gives a "maximum range" at the set angle. The ChaG app only gives me the maximum range at the ideal angle to reach as far as the pellet can.
Well, the two calculators do not agree: :(
I enter into ShoC the ideal angle for max. range that ChaG gives me (25 degrees) and tell ChaG to use the G1 drag model. The result ShoC gives me is 324y. However, ChaG tells me 366y.
That makes quite a difference for the houses around my shooting area....
And this is even using the wrong drag model (G1, for bullets) instead of airgun pellets' GA.
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Now what?!
Well, outdoorman :D , thanks for sending me to Shooterscalculator. It made me try different things out, and finally comparing what I got to the Windows version of ChairGun4 -- and voila!
The WIN program ChairGun does have a maximum range calculator, for any angle, even 90 degree up! I love it -- just wished this function was on the app as well to carry in my pocket!
How to get there:
Enter all your pellet and gun data as usual.
Then from the menu select Toolbox.
Select Maximum Range.
Then I get the choice of a table or a graph.
The table has all the info (the second column called Range (x) (Yard) is the maximum range -- the "range" in the fifth column I do not understand.
To have more or less detailed angles displayed, I can right click in the table; that brings up the context menu to select "Show every" yard, or 10 yards, etc.
I printed the table to take with me on my cell phone -- I used a program to print to PDF.
The graphs are very helpful, too. Rightclick into the graph and it gives you the context menu to select from:
• Ballistic Envelope (max. range and max. altitude [height over ground] combined)
• Max. Range
• Max. Height [over ground]
• Elapsed Time
• Terminal Velocity
I saved the images to take with me on my cell phone as well.
(Unfortunately I can't save the pictures in a location of my choice, I need to go to the ChaG directory c:\ProgramData\ChairGun4\Images\ and copy them to a place of my choosing.)
(Also, APP-ChaG gives me the *terminal energy* when hitting the ground (or some object I rather not damage), 0.44FPE. Unfortunately, WIN-ChaG only gives me the terminal velocity -- would be great to have that chart + graph available.)
(Taken the files with me instead of calculating them on site of course gives a slight error because of the difference between the actual atmospheric conditions and those entered when calculating the data for the files in WIN-ChaG.)
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I compared the maximum range I got from the APP-ChaG (390y at 25 degrees) with the number from the WIN-ChaG -- 388y at 28 degrees, at 25 degrees the range is 387 (both with GA drag model; I made sure it put in the same atmospheric conditions). Well, that's close enough for me!
From now on I'll be carrying these data as files on my cell phone with me, so I can keep my angled shots free of nearby structures -- just in case I miss. Using GoogleMaps with the Measure Distance feature I can measure the distance to those structures easily.
Pigeons high up in the trees, watch out, here I come! 8)
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Great info Matthias, this will probably help others.
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Here is one of the graphs that ChairGun spit out for me with the maximum range of a JSB at 15.6FPE / 665fps MV.
"Here" – well, I'm still learning, I guess I haven't figured out how to post pictures on GTA yet, so, it's in an attachment. Hope it works.
And here's the table (another attachment) with the detailed data (I copied the CSV file into CorelDraw, added a title, and saved it as JPG). (The data are a bit different from the ones in my previous post, because I adjusted the atmospheric conditions to our local winter – down South of the Equator where I shoot we are in the depth of winter.)
How I think I will use this now that I found this:
Say, there is a group of houses close by that I try to avoid hitting in case I miss my target. And let's say, the houses extend all the way from where I shoot to about 250 yards away from it (I ranged that with GoogleMaps).
Then with one quick look at the graph I can see I have to shoot at angles from 5 to 64 degrees with this pellet-gun combination – so that in case I miss my target my pellet drops beyond the houses. (Sure, let's give it some margin for wind and all that...).