Author Topic: Long range ancillary equipment for airgunners  (Read 3577 times)

Md25v

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Long range ancillary equipment for airgunners
« on: January 26, 2016, 02:24:03 PM »
Towards the end of last year I made a pretty big mistake. I left my airgun notebook at the range, along with all the ballistic notes for the past 18 months on three airguns. Since I have to start a new book and just joined this new forum I figure I could share my set up.
I started my new notebook just after the new year and have only been shooting twice this month due to work schedules and the highly uncooperative weather. I'm going to post the first few pages which have not been filled out yet just to show the setup for my airgun logs. One thing that is not shown in the pics is all the data on the airgun itself like scope height, cleaning log, tune info, etc...
The following pages are not filled in yet as this is a completely new book.


Zero Summary Chart
This page tracks the movement in my zero with TEMPERATURE
I have similar pages for HUMIDITY and BAROMETRIC PRESSURE as well



This page is my quick Ret reference.
I am currently using a 2.5-10 power scope on this particular airgun.
I keep one page for 10x and one for 5x.
THE MAGNIFICATION TRACKING OF THE SCOPE IS NOT PERFECT so the 5x page is not simply twice the 10x page. It is actually 1.8x of the 10x so the scope does not match up perfectly to the numbers printed on it. Knowing things like this will allow you to get the very best results from your equipment. (Unnecessary if you have a first focal plane reticle)
The lowest power (2.5x) I really only use for close range and night vision hunting inside of 50 yards.



This is the 5 shots I took to verify my zero on the last range trip. There were several people shooting muzzle loaders and the smoke was quite a distraction. The flier was a complete miss on my end of checking the wind flag. It is important to write down the starting fill pressure for eash session as well. I took that pic before writing that I had just filled the gun to 2900spi.



I want to also mention my secret weapon for long range shooting. I do NOT use the Hawke software for airguns (Chairgun). I find the B.C.s they list to be very inaccurate and when shooting past 80-100 yards it becomes very apparent. I use ATrag software from Horus. I put in the B.C. estimated by the Hawke program and set the ATrag to "verify mode". The way it works is you input all the environmental data directly from a kestrel weatherstation and then shoot a pellet of two long range, say around 150 yards. It will predict the impact based on the B.C. that you input and then you tell it how far off it was and it re-writes the B.C. in the formula and allows you to save it. From that point on it will adjust the functional B.C. (which changes in flight as speed decreases) every time you update the weather and environmental factors.
I HIGHLY recommend that software and the Kestrel 3500 combo. 

I will add to this in Feb as I am able to get to the range again. We just got 3ft of snow this past weekend so it will be a week or two before the range is clear.


P.S. I have a FLEX coming and can't wait to see what it can really do at long range!!!




oldpro

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Re: Long range ancillary equipment for airgunners
« Reply #1 on: January 26, 2016, 03:40:13 PM »
 Holy Crap you are dead serious!!!! I love the detail you put into your shooting.

rsterne

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Re: Long range ancillary equipment for airgunners
« Reply #2 on: January 26, 2016, 04:30:02 PM »
What ballistics drag model does the ATrag software use?.... Is it the G1, or something else?.... How accurate is it for pellets, and over what range of velocities?.... My experience has been that pellets do not match any of the current drag models, particularly in the transonic range (Mach 0.8-1.2)....

Bob
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Md25v

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Re: Long range ancillary equipment for airgunners
« Reply #3 on: January 26, 2016, 06:38:20 PM »
O.P.- Yeah, and it still kills me that I left a year and a half worth of data at the range. This time I am backing up everything to an excel sheet just to be safe.

Bob- The ATrag uses a variable drag model that actually changes across the different velocities. Its not as simple as a G1 vs G5 for flat base an boat tail bullets. The variable drag model was originally in the Sierra software and in the old version you start with a G1/G3 etc and then adjust based on differences from expected point of impact at range. The new version, as well as the Horus Software have a drag profile starting point in the equation but the way they work is by re-plotting the actual arc of the bullet/pellet based on the real world impacts it gives an exact arc profile (and automatically adjusts it for changes of B.C. in flight) instead of trying to match a pre-programmed drag profile. The two things that most software don't calculate well are (1) every projectile's B.C. changes with changes in velocity, and (2) During trans-sonic flight many low B.C. bullets don't actually destabilize but instead their functional B.C. changes and they deviate from the predicted arc if that arc is based on a consistent drag profile like a G1,etc

It has been VERY accurate with the heavy 34gr .25gr JSB Heavies out to 200 yards and has given very predictable adjustments throughout the day as the temperature and humidity changes over this past summer. It even allowed me to take a crow at 182 yards in only 2 shots with my Hot Rodded TalonP
« Last Edit: January 26, 2016, 06:44:23 PM by Md25v »

rsterne

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Re: Long range ancillary equipment for airgunners
« Reply #4 on: January 26, 2016, 06:51:12 PM »
All very true, which is why I asked the question.... Not many people understand that a bullet's BC changes over quite a wide range as the velocity changes.... Well, actually that's not technically correct, it's just that the Cd profile of the bullet doesn't match the drag profile of the model being used to calculate it.... If it matched perfectly, then the BC would be a constant.... as it would be for a G1 projectile compared to the G1 model.... Of course the G1 drag profile is anything but "constant", the Cd varies a huge amount, particularly in the transonic range....

So are the BC's that the program spits out stated as G1 Ballistics Coefficients?.... or does it not output a BC at all, and just comes up with it's own Drag Profile for that particular pellet/bullet and then uses that for all it's calculations?.... Both methods will produce the same results, but if you want to compare to some other bullet's BC (at a particular velocity), then you have to use the same standard for both....

Bob
« Last Edit: January 26, 2016, 06:52:52 PM by rsterne »
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Md25v

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Re: Long range ancillary equipment for airgunners
« Reply #5 on: January 26, 2016, 07:02:35 PM »
Hope I am answering what you're asking correctly. When you enter the "Verify" mode and input a new point of impact that is different from what was predicted off the original G1 drag profile (which is way off for pellets at any velocity) it recalculates the arc to match the new point of impact and in the space that originally listed the B.C. it now says CST for custom. Unfortunately, how it creates the new arc isn't something that the limited readout on the PDA tells you. So while you initially enter a B.C. to predict the ballistic arc once it goes into "verify" mode it no longer lists a B.C. on the screen.
This is the device I am referring to if you are interested. Although I will tell you that their sales people are not very good with how it actually works.
https://www.horusvision.com/pda.php
The new Sierra program works the same way and their call line will actually transfer you to the software engineers who are willing to talk at length about how it works.
 https://www.sierrabullets.com/products/infinity-software/index.cfm
« Last Edit: January 26, 2016, 07:04:46 PM by Md25v »

rsterne

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Re: Long range ancillary equipment for airgunners
« Reply #6 on: January 26, 2016, 07:13:57 PM »
OK, I understand.... It's starting with a G1 BC that you input, and then correcting it based on whatever POI data you input.... I assume the more data points you give it (ranges) the better it refines the trajectory.... Ultimately, what it's doing is calculating a Cd curve, refining it, and then using that to predict everything else.... Pretty slick!!!.... Can you input downrange velocities instead of POI?.... How many points can you input?....

I assume it can give really good predictions for wind drift as well, once it has the Cd curve figured out.... I hope to eventually get a LabRadar and then I can make direct velocity measurements every 1/2 yard, and produce an extremely accurate Cd curve for any bullet/pellet with only a few shots (at different velocities).... Once you have that Cd curve, everything else falls into place, once you know the muzzle velocity and range (and wind)....

Bob
« Last Edit: January 26, 2016, 07:15:40 PM by rsterne »
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Md25v

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Re: Long range ancillary equipment for airgunners
« Reply #7 on: January 26, 2016, 07:19:54 PM »
Thats exactly it. It really doesn't benefit from many impact points as much as it does from two really far points. I input two shot from a .22lr rimfire at 400 yards when I first got it and it was spot on at every range from point blank out to 400. I ran out of cant and scope adjustment after that. and yes, the wind predictions are excellent. Much more precise than I can call by flags and mirage.

oldpro

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Re: Long range ancillary equipment for airgunners
« Reply #8 on: January 28, 2016, 04:49:41 PM »
 Ow NOOOO Now im never going to get any sleep....One more thing to mess with and get the squirrels in my head running around. ;D

Monkeydad1969

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Re: Long range ancillary equipment for airgunners
« Reply #9 on: February 03, 2016, 01:24:55 PM »
I see you guys are speaking Chinese again... :o
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Re: Long range ancillary equipment for airgunners
« Reply #10 on: February 10, 2016, 07:12:38 AM »
   I agree MonkeyDad, I just shoot and take notes of distance and fill pressures lol Too much work with the programs. This old guy is not too computer savy!!! It's so cool to see how these guys can nearly pin point where that pellet will impact off a computer.
  Best of Luck Fellas

Windmeister

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Re: Long range ancillary equipment for airgunners
« Reply #11 on: February 11, 2016, 06:33:27 AM »
When recalculating a parabola curve, or the ballistic curve if you will, with any drag model (G1 or otherwise) as the base, you will be using some sort of predifined spline/curve profile, be it bezier points, or something else. So as long as you can correct the POI after the fact, recalculating the correct curve at that distance should be simple, and probably distances within 20% of that would be dead on.
As for the wind component, I would think that the re-calculated curve is feeding the new numbers to the algorithm that figures out the drift.