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Big Game Info Ballistics calculator.

 
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  #1  
Old 02-09-2005, 02:47 AM
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Big Game Info Ballistics calculator.

It appears that our new member Klinkers has developed a handy ballistics calculator available on line. (see The first topic in this topic section for the link.)

It is my intention to begin this post for discussing questions, suggestions and comments concerning this program with its author. Mostly because I have a bunch of questions that someone else might also have.

It is not my intention to bash or argue about any points of this site. If you don't have constructive input please don't put IT in here. If you find something that you dissagree with politely make your point and let it rest. Klinkers was nice enough to share this with us. His site asks for suggestions and comments.

I have taken a brief look at the site and I would like to start with a few questions.

1. Elevation as it relates to the sight relationship to the gun. I guess I dont understand what this is all about. At first I thought it meant altitude. It became obvious that this was not right. Then I thought it meant the distance from the center of the bore to the center of the scope. I'm not sure if this is right. Could you please explain what "elevation" means exactly on this site. I looked in the glossary and this did not clear it up for me.

2. When calculating recoil, what does the "velocity" window represent? Is this the theoretical rearward velocity of the gun if it were mounted to a weightless carriage rolling on frictionless bearings? Is it measured in feet per second?

3. If I set the maximum range at 2000 yards I get a message that the maximum incremental drop is exceeded. What does this mean?

4. How do I know which drag function to choose?

5. Are the 3 windows under "B.C." and "Vmax" so that we can enter the BC for the given bullet at different velocities like those given on the Sierra bullets website? If not then what do they do and what does "Vmax" mean?

Now I have one suggestion. It would be nice for us knob crankers to be able to see our come ups in "MOA+ clicks" instead of just clicks. By this I mean if my come ups for X distance is 14 clicks and my scope has 4 clicks per MOA I would like to see 3+2 (or 3MOA plus two more clicks) if my come ups are 49 clicks the column would show "12+1". This saves doing the math wrong because at 1000 yards 7 clicks is a 23 inch miss. 27+3 is alot easyier to crank in than 111 clicks.

Lastly a comment. On your site you say "You will find on most if not all american made scope that the reticle is magnified as power is adjusted."

I'm not sure this is quite accurate. I have owned Leupolds and Weavers and Bushnell and Tascos. As a gun store clerk I have sold many other brands and I can only think of one scope that had a reticle that grew as the magnification increased. I'm sure there are more but I don't think it is most and it is certainly not all. Unless you mean something different.

Klinkers I know I didn't ask you if you wanted to have this post so if you don't want to handle questions like this say the word and I'm sure we can get one of the moderators will nuke the whole post. [img]/ubbthreads/images/graemlins/wink.gif[/img]
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  #2  
Old 02-09-2005, 06:03 PM
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Join Date: Feb 2005
Location: Iowa / Missouri
Posts: 29
Re: Big Game Info Ballistics calculator.

I truly do welcome any and all comments and suggestions and will be more than happy to try to answer your questions.
1) Elevation that I refer to in my calculator is the angle of the bore relative to Line of sight to produce the input zero parameters. This corresponds to the discussion that JBM had regarding use of his website in "Ballistics Problem" thread.
2) The recoil velocity is conceptually as you described it.
3) The calculator engine is based on the work JBM has up on his web site, I simply ported it to a different language to make it easier to put nice frontend on it. The reason I bring this up is that I don't purport to be a mathemtician, I'm a programmer. His library code that I ported exits the calculation loop when the calculation error exceeds a program constant. Depending on the input load parameters this will occur at various ranges. This is the same thing that occurs on Brad's site, with the default parameters and a range of 2000 yards, 1800 is the last row containing data, I just don't display the rows with zeros. If Brad reads this perhaps he could explain it more completely.
4) The selection of drag function depends on what you have for input or what you would like to try as a more suitable model for your situation. As a general rule the bullet makers quote BCs as G1 which is the default. If you find that the calculated trajectory doesn't compare to what you find in the field, you may well find that using a different model will more closely match your field results. Unfortunately, for most of us, this is a trial and error process. By changing the drag model and the BC values you should be able to come very close to your field results. You must also input the Atmospheric conditions as close to reality as you can. The more accurate your input the more accurate the output. If you have the abilty to measure multiple velocities or time of flight you can use the BC calculators on Brad's site to get BC values for the different drag models.
5) You are exactly correct, the multiple rows allow you to enter BCs for velocity ranges like quoted by Sierra. It's just one addtion I made to allow you to get the calculations to match reality.

The quote about the crosshair magnification is obviously incorrect, if you could tell me where you found that I will correct it.

Finally, it would be very easy for me to provide another display option for comeups, wasn't aware that was the easiest way to think about them. I hate to admit but I'm a better programmer than marksman and don't usually stretch out there far enough to need comeups (yet).

I've considered writing a user manual for the advanced calculator but have hesitated because the basic calculaor
is used probaly 3 or 4 times as much as the advanced version. If there is interest I'll write one up.
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  #3  
Old 02-09-2005, 10:57 PM
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Re: Big Game Info Ballistics calculator.

Hello again Klinkers.

In regard to my first question I just don't get it. I do this every once in a while. It's like looking for my sunglasses then finding that I'm wearing them. If I have a scope that is mounted on a tapered base as opposed to one that is parallel with the reciever (and the barrel as well) you are saying that I enter the negative degrees of that base? Dosen't my line of sight change minutely as I adjust the elevation of my scope?

I thought that the "elevation" in the other post related to feet above sea level. Not the angle of the line of sight.

This is just a mental roadblock for me I guess. If you could give me an exaple of what you mean that might help a lot.

Questions 2, 3, 4, 5. I read you loud and clear. Thanks.

[ QUOTE ]
The quote about the crosshair magnification is obviously incorrect, if you could tell me where you found that I will correct it.

[/ QUOTE ]

Skills: Ballistics: sighting in: Paragraph 3

[ QUOTE ]
Finally, it would be very easy for me to provide another display option for comeups, wasn't aware that was the easiest way to think about them. I hate to admit but I'm a better programmer than marksman and don't usually stretch out there far enough to need comeups (yet).

[/ QUOTE ]

That is how I list come ups on the ballistic charts I bring to the field. Some scopes have 1/4 MOA per click and others have 1/8 MOA per click so there might be an option for both. A column that shows come ups in MOA rounded to one decimal place would be fine. Heck make a new post explaining a number of options and follow it up with a Poll to see which one these members like most. Dont forget an option for "Other"

[ QUOTE ]
(I)don't usually stretch out there far enough to need comeups (yet)

[/ QUOTE ]

Stick around for a while, it will start to grow on you. Clicks at 200 yards are simple enough but as I mentioned, come ups at the ranges these guys are shooting are CRITICAL and no place for a math error or losing count when shifting position.

[ QUOTE ]
I've considered writing a user manual for the advanced calculator but have hesitated because the basic calculaor is used probaly 3 or 4 times as much as the advanced version. If there is interest I'll write one up.

[/ QUOTE ]

The many that don't use it dont mind what they are missing. The few of us that know what they are missing would brobably find it a nice reference to have. Are you thinking something like a Printable PDF file (adobe acrobat sorta deal) Sorry I am not wise in the ways of computer lingo.

I hope the other members give you some input here to help you along with your program. ( of course it is worth what I paid for it [img]/ubbthreads/images/graemlins/wink.gif[/img])
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  #4  
Old 02-10-2005, 12:48 AM
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Join Date: Sep 2004
Location: Ogden, Utah
Posts: 81
Re: Big Game Info Ballistics calculator.

4ked horn
thanks for a great post. It is refreshing to see someone with questions polietly request explanatins. I certainly got a lot out of the exchange and will follow the thread with interest.
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  #5  
Old 02-10-2005, 12:55 AM
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Join Date: Sep 2004
Location: on the rifle range in Utah
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Re: Big Game Info Ballistics calculator.

4kedhorn,
I couldn't have said it better myself. Excellent advice for the programs-especially the suggestion of MOA for us knob twisters.

My scenario in the other thread was for elevation as you thought. I asked about that problem because I print off drop charts for local friends for them to take deer hunting, and I am seeing a problem as mentioned with the programs. If I zero their guns for a certain range here at my house (4800 ft) and then they take their rifle to 10000 feet on the deer hunt, the rifle's angle of line of sight stays the same (nothing bumped the scope or bases), but the thinner air makes the bullet hit the line of sight farther out than before and therefore your gun is no longer Zeroed were you think it is. Does this program of Klinkers fix this?

P.S. I just aquired Oehlers ballistic program (that now makes 7 programs I own) Ballistic Explorer. I haven't really figured the whole program out yet, but so far as I can tell, it DOES account and refigure your trajectory properly. Need more time with it to be sure.
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  #6  
Old 02-10-2005, 05:25 PM
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Join Date: Feb 2005
Location: Iowa / Missouri
Posts: 29
Re: Big Game Info Ballistics calculator.

Think of elevation like this: the path of your bullet crosses your line of sight at two points in it's travels, once fairly close like around 25 yds out and again at your zero range. The elevation is an angle expressed in moa to get that bullet to rise above the line of sight. If you zero your rifle @ 100 yds the angle is x moa, @ 300 it is obviously greater than x moa to get the bullet higher above the line of sight so it comes back down to the los at the longer range. The trajectory curve always stays the same, assuming all other factors remain constant, you are just moving the poi by changing this angle. Since you're "knob cranker", think of it as the comeup to acheive your initial zero.
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  #7  
Old 02-10-2005, 05:45 PM
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Join Date: Feb 2005
Location: Iowa / Missouri
Posts: 29
Re: Big Game Info Ballistics calculator.

You can produce comeup charts adjusted for different conditions using the advanced calculator. Simply calculate your desired zero, enter appropriate field conditions, and click the calculate button. Between the tab object and the trajectory table you will see "Elevation 5.784 moa" or whatever the actual calculated value is. Enter the number into the Zero Elevation textbox. With a non-zero value in this field any changes you make to Atmosphere, Incline, etc will be calculated based on your initial zero value.

To implement your example, you would adjust the atmosphere for the 10000 ft altitude, recalculate and see what the trajectory will be up on the hill. Just be aware that when you enter 10000 ft altitude and click std conditions they undoubtedly will not match the actual conditions in the field.

This situation is what prompted me to create a PDA program. Imagine the notebook full of trajectory tables that would be required to accurately predict point of impact across all the real world conditions you could encounter on a hunt. If you're only shooting out to 300 yds or so it's a non-issue. The farther out you go the more critical it becomes. With the PDA, it's as accurate as your input parameters.
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