G1, G7 Ballistics Coeficient?

#51
Re: G1, G7 Ballistics Coeficient?

Gotcha Bryan,

<span style="font-weight: bold">You win,</span> unfortunately perfect doesn't exist, not for the end user at least. We'll ignore the early contradiction to that statement made by you.

But I completely understand what you are saying, with the caveats, in a perfect world this is better. With a perfect trigger pull, perfect muzzle velocity, perfectly steady wind, perfect range, etc etc...

perfectly acceptable answer to me. When you get the perfect program let me know, I'll buy it along with others I'm sure. Until then we'll all <span style="font-style: italic">"tweak" </span> a little even the G7.

I'll move on and we can consider ourselves lucky it only took 50 years for this realization, thanks Bryan, you Sold Me.
 
#57
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I'll buy that. </div></div>

me too.....
smile.gif
 
#58
Re: G1, G7 Ballistics Coeficient?

First - thanks to all who participates and contributes knowledge to this discussion.

Bryan, I'd very much appreciate if you could answer my questions about Pejsa in more details. In particular:
  1. I thought that Pejsa <span style="text-decoration: underline">stops</span> working (becomes too inaccurate) when bullet velocity slows down to transonic, and that was the price for reducing complexity to algebraic equations. Is it incorrect?
  2. G1 BC tells how much the bullet differs from Type 1 projectile. Since Pejsa does not take Type 1 standard curve as a starting point - what good can G1 (or any other G) possibly be for it?

Let me explain why it bothers me. There are two approaches to trajectory computation. One is direct: you input everything you know about this bullet - and compute where it's going to be at every second of its flight (nice, but computations are quite expensive). The other one is to use a reference to already-done drag curves computed for Standard Projectiles: you input your "difference" from that projectile in form of BC - and get your trajectory (simple, easily computable - but accuracy of prediction depends on how similar the bullet is to the standard projectile it's compared with).

It seems to me akin to asking a question: "Where am I?" One answer would be "You're exactly at 41N02 and 70W05" - direct. Another one would be "You're exactly 4.5 miles SSE from reference point X which is at 41N03 and 70W06" - using Point Mass approach.

My big Pejsa question is - what good for direct solution is the knowledge that "you're G1=0.456 off the G1 standard" if you don't use that standard anyway? How does knowing that you're 5 miles SSE of an unknown point help you?

Or is it a combined solution with Point Mass <span style="text-decoration: underline">and</span> Pejsa under hood? If it is - why not just admit it? If it isn't - then what is it, how does it work, and why/how can it use Gx coefficients?


Frank, Gus <span style="text-decoration: underline">didn't</span> say he didn't tweak the equation and BC (and that's what Bryan meant, I'm sure) - he said he did not tweak the Lapua <span style="text-decoration: underline">radar data</span>. Which makes sense.
 
#59
Re: G1, G7 Ballistics Coeficient?

As far as i understand (might be completely off as its only a hobby to me) pejsa equations are also function based (model; the same stuff as Gx functions). So also in this case what you do is "forecast" a bullet path based on initial set of data (BC, speed, atmo, etc...) which are processed by using a fixed/predetermined model. The issue i see is where the tweaking is done (and if at all necessary) do you change initial set of data to "fool" the model to produce expected (measured/observed) results or do you change/program the model so it outputs observed/measured value. Or as Lowlight pointed out is it even viable to change the model as there is NO model in the world (at least for complex stuff) which is a perfect fit and works.
 
#60
Re: G1, G7 Ballistics Coeficient?

I have the complete email from Gus, but suffice to say, he answers part of that this way... it goes to how his program handles the information internally, my point is, his data was not tweaked externally, which he says is considered "cheating"... adjusting the model internally is not "tweaking" in my opinion, especially if the end results are correct.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">As we all know, actual Doppler is the best source for downrange data.
Nothing comes close to that. (no human error among other things which are
completely unreachable for a human shooter), and as such constitutes the
only credible baseline for comparing predictions.

Please find attached some new slides based on Doppler data for the .50BMG,
provided by the Spanish Army (now they are running LB3 with their SF forces,
and the Brits adopted it for ALL services and is now fully operational),
plus Lapua's own Doppler for the .338 LM

You can use the DRAG ANALYSIS (ANALYZER module) just to visualize how the
different G functions work for the same data.

Having said that, LB3 ballistics engine, can and will handle ANY G function
(but for the sake of convenience only G1 and G7 are supported), since the
engine DOES NOT RELY on ANY PARTICULAR G function at all...contrary to the
"POINT MASS"

I have said this many times, but one more will not hurt. LB3 ballistics
engine IS NOT PEJSA.

The Doppler data I provided was not tweaked at all. In fact, all the inputs
used are in the article for anyone willing to make its own run and further
comparison,. Tweaking is, in this case, cheating to others and to myself.

LB3 engine is a very complex algorithm to discuss the details in a short
email, but enough to say, that it models the Drag Curve for MACH number
using the provided BC as an initial "entry point".

After that, the ballistics curve is computed ACCOUNTING FOR the "history" of
the bullet's flight, from point A to point B. In short, the engine knows
what happened before in order to make the next prediction.

Contrary to what others could say POINT MASS does not
account for that.

It's important to realize that while the POINT MASS engine is used by almost
any program, not all implementations are the same. Some are better than
others. That's one of the reasons to see different outputs among two
programs using the "same" PM method.

The other VERY important one, is how they handle the ATMOSPHERE algorithm in
order to compute the AIR DENSITY RATIO (from the usual parameters or Density
Altitude). </div></div>

I can always get more information from him, or even point him to this thread if he hasn't already seen it. But in my mind he answers it pretty well, I would say, yes he is using a model unique to LB3, but again my only interest is the final result. Personally don't care how you code it, as long as the bullet hits the target. If you are coding it to channel Zeus and it gets you the hit, that works for me.
 
#61
Re: G1, G7 Ballistics Coeficient?

I hesitate to continue this discussion as it's been one of the most peaceful and productive I've seen on this site. Leaves me feeling all warm and fuzzy inside.

But your questions are good ones so I'll try to answer.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I thought that Pejsa stops working (becomes too inaccurate) when bullet velocity slows down to transonic, and that was the price for reducing complexity to algebraic equations. Is it incorrect?</div></div>
Pejsa's 'main' equations, the ones published in magazines, etc, are only for supersonic. If you follow that curve down too far in velocity, it continues to go up and up to infinity at Mach 1, whereas actual drag curves inflect at transonic, peak near Mach 1.0, and go back down for subsonic.
So one of the 'judment calls' in Pejsa solvers is deciding at what velocity you choose to <span style="font-style: italic">splice</span> the supersonic curve/equations to the transonic curve/equations. Pejsa actually represents transonic drag with a flat line (see the image at the beginning of this article: http://www.pejsa.com/articles.htm)
Then, there are a different set of equations you splice in for the curve/line down to subsonic, then another set of equations for subsonic. Each of these curves requires a number to scale the drag, and the curved parts also need numbers to shape the curve (the DK variable in LB3). Based on the BC you give the program, it chooses the scalar values which place the supersonic drag curve. The transonic and subsonic lines are related to the top of the supersonic curve according to it's value where they splice.

Since no information about the G1 curve is contained anywhere in the pejsa equations, an assumption is made about what speed the BC input is valid for (I forget if the programmer has control over this, or if it's implicit in the equations) and the curve decays it from there according to the DK value you give it. I *think* it might consider the BC you input as valid for the MV you enter, then decays from there. So you could be on two entirely different curves with the same BC depending on what MV you use.

Suffice it to say, the pejsa solutions are not all assembled the same because of the freedom afforded to the programmer about what velocities to splice the different segments. This makes it possible to structure a solver around one set of data and make it work perfectly for a single BC/DK pair. But now your entire solver is 'flavored' by that data set, and it won't an accurately represent other types of bullets.

Given this hodge podge of a program, it can appear to work pretty well with normal G1 BC's. How's that possible? Because the program assumes the BC you give it is valid for your MV, and decays it from there. This works conveniently with commercially advertised BC's because they're usually high to begin with. In other words, rather than working right with properly defined BC's, the pejsa equations offset the error of the inflated BC's by decaying them internally. So you can get a decent answer using an inflated BC and a solver that decays it.

I have no idea what mods exist in LB3 that makes it not Pejsa. I'm not even interested because unless a solver uses standard drag curves, it will not be able to properly interpret the BC's which are referenced to standard drag curves. In other words, there's no standard way to describe bullet performance to a non-standard solver.

whew.
 
#63
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan</div><div class="ubbcode-body">Pejsa's 'main' equations, the ones published in magazines, etc, are only for supersonic. If you follow that curve down too far in velocity, it continues to go up and up to infinity at Mach 1, whereas actual drag curves inflect at transonic, peak near Mach 1.0, and go back down for subsonic.
So one of the 'judgment calls' in Pejsa solvers is deciding at what velocity you choose to splice the supersonic curve/equations to the transonic curve/equations. Pejsa actually represents transonic drag with a flat line (see the image at the beginning of this article: http://www.pejsa.com/articles.htm)
Then, there are a different set of equations you splice in for the curve/line down to subsonic, then another set of equations for subsonic. Each of these curves requires a number to scale the drag, and the curved parts also need numbers to shape the curve (the DK variable in LB3). Based on the BC you give the program, it chooses the scalar values which place the supersonic drag curve. The transonic and subsonic lines are related to the top of the supersonic curve according to it's value where they splice.</div></div>
Could you please point me at the source of (a) transonic and (b) subsonic equations? I don't think I remember seeing those (though of course they must exist
smile.gif
)... Is it the Almighty McCoy? And are those equations linear or differential?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan</div><div class="ubbcode-body">I have no idea what mods exist in LB3 that makes it not Pejsa. I'm not even interested because unless a solver uses standard drag curves, it will not be able to properly interpret the BC's which are referenced to standard drag curves. In other words, there's no standard way to describe bullet performance to a non-standard solver.</div></div>
Well, I am interested because LB3 seems to give good predictions - so I'd like to know what Gus tweaked to accomplish it.

But I'm totally with you on the standards, and the need for a standard way to describe bullet performance across the board. May not be as important in the field where all I need is an accurate impact prediction regardless of where it comes from (say, Zeus-channeled
wink.gif
). Definitely important when I'm at my desk comparing various aspects of bullets performance, deciding which bullet to pick for the next bunch of loads that would suit my purposes best.
 
#64
Re: G1, G7 Ballistics Coeficient?

Mouse in that case you want LB3, and its analyzer as noted in the email excerpts.

LoadBase_Modules.jpg


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">designed as a set of calculators, ranging from Interior Ballistics calculations to other related phenomena, like computing a barrel’s optimum twist, a bullet’s stability factor, BC from two velocities, BC conversions between different Drag functions and to calculate the Drag Coefficient as it’s needed by the ballistics engine.

<span style="font-weight: bold">Its value as a module is central to this program, which is projected to perform side-calculations that while not routinely done, are of great importance for the precision shooter.</span>

Powley Calculator : an updated implementation of the method devised by the late Homer S. Powley to predict load charges and pressure when data for a particular cartridge is not easy to find. A nice complement for the extensive loads’ database provided by LoadBase 2.0© providing to the experienced handloader a fast, accurate predictor.

Twist & Stability : an enhanced tool to compute a barrel’s optimum twist and the resultant stability factor for a given bullet. Two methods are used at the same time. A modern one, considered a breakthrough in modern ballistics, based on the work of Don Miller ( 2005 ) which has been proven very accurate. This method considers the effects of both velocity and air density. The second one was derived from the work of Sir Alfred Greenhill ( 1879 ), however the current algorithm was enhanced to deal with new bullet styles and high velocities. It does not use a constant value across the range of the different variables.

Chronograph Vel Correction : its purpose is to correct the instrumental velocity (chronographs figures ) accounting for the BC of the bullet, its velocity and the distance between the muzzle and the sky-screens.

<span style="font-weight: bold">BC from velocity : The BC gives the ratio of ballistic efficiency compared to the standard G1 projectile as used by the bullet’s makers. This module will accurately compute any bullet’s BC given its velocity loss measurement as indicated by two chronographs.</span>

<span style="font-weight: bold">BC Conversions : since there are many drag functions that were developed to have a better fit for same bullet styles, this tool will allow the user to easily convert one function’s value to another very easily. A must for those interested in pursuing very accurate trajectory predictions for the modern, streamlined bullets.</span>

Drag Coefficient : this module was specifically added to assist the shooter to determine the correct value of a critical constant used to calculate the changes to the drag function over the supersonic velocity range. In other words, this program ballistics' engine uses a drag coefficient (DC) that affects the calculated rate of bullet deceleration. Applying this DC, the resultant trajectory calculations are very accurate for that particular bullet because the drag function has effectively been tailored for that particular bullet.

Recoil Calc : here the user will access a recoil calculator for up to two firearms, projected to perform accurate and meaningful comparisons, in both tabular and graphical layout, featuring an straightforward interpretation of this central effect.
</div></div>

Since LB3 is both a desktop and mobile program, you can work in one and transfer information to the other.

LoadBase3_Mobile_Analyzer_BC_Data.png


LoadBase3_Mobile_Analyzer_BC_Results.png


This analyzer feature is what you are looking for in my opinion
 
#65
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Could you please point me at the source of (a) transonic and (b) subsonic equations? I don't think I remember seeing those (though of course they must exist )... Is it the Almighty McCoy? And are those equations linear or differential?</div></div>

Pejsa's equations aren't covered in McCoy. You have to get Pejsa's book.

It looks simple at first (like only having one set of closed equations to apply). But then you find out you need a whole different set for transonic, another for subsonic, each with their own bullet performance metrics, it's a quagmire. Then you find that the BC you're giving it isn't really a BC, but instead is... something else. Then there's the DK; just come up with that... somehow, for each bullet, or just use the same one for all bullets, whatever you feel like doing to give the program a little bit of personality.

If you really want a headache, just get his book and read it. Then you can code you're very own, unique, one of a kind ballistics program!

And when you get tired of tweaking it for each and every bullet you shoot, you can just go back to what everyone agrees is the 'best possible' solution: standard G7 BC's and a point mass sovler.
 
#66
Re: G1, G7 Ballistics Coeficient?

Frank, you're right - theoretically that's what I would want, and the advertised capabilities of LB3 are impressive (though I'd have to run Windows in a VM on the desktop, and mobile-Windows mobile device is not in my plans for the next decade).

But one of my shortcomings is having a long memory for slights, and the brush-off answers I got from Patagonia did not entice me to give them my money (even though their product seemed good). I didn't want to think what would happen if - God forbid - I'd need support from them. Yes I know <span style="text-decoration: underline">you</span> were getting great support from them - but that <span style="text-decoration: underline">observably</span> didn't translate to me. Also, I really prefer to know/understand the working of the tools I use (and leave Black Boxes alone).

Take Bullet Flight for example: not only am I happy with the program itself (so far
smile.gif
), but Robert answers my emails almost always the same day. That's the kind of support I can rely on (unlike Ballistics FTE - which is a very good program capabilities-wise, but not supported as nicely).
 
#67
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Also, I really prefer to know/understand the working of the tools I use (and leave Black Boxes alone).</div></div>

I used to be that way. In fact, one of the reasons I got an electrical engineering degree was because I wasn't satisfied with the answers I got to some questions about electronics.

However, probe deep enough in any field, and you'll find things which you just have to take on faith.

The usefulness of any computer model is whether it produces valid predictions. (One which doesn't is useless - take climate models used to predict global warming, for example.)

So, I'm happy with a ballistic program which does that. I don't care how it works, unless I plan to write one, and after retiring from a career of doing things like that, I wouldn't touch that with the proverbial ten-foot pole.

Your mileage may vary. I don't mind.
laugh.gif


 
#68
Re: G1, G7 Ballistics Coeficient?

I use all Macs myself and have one of my iMacs dual booted to Windows using bootcamp to run the Windows stuff. Then I just have an iPaq.

I like FFS because it's a chip not dependent on any program, you just insert, like i have a Trimble Nomad that I got on sale at USCAV, less than $1k, so it has all the features and I can simply pop a chip in an not have to back it up to anything.

But like Bryan said, I always have my iPhone on me or even usually an iPod close by, so doing it the other way with a calculated G7 or G1 (banded) works.

But I keep a lot of it on hand because people ask and I want to be able to give reliable answers.

I understand Gus is working on a Window 7 Phone program that is supposed to have more horsepower than the PDAs.
 
#69
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">I used to be that way. In fact, one of the reasons I got an electrical engineering degree was because I wasn't satisfied with the answers I got to some questions about electronics.</div></div>
It seems that we understand each other.
wink.gif


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">However, probe deep enough in any field, and you'll find things which you just have to take on faith.</div></div>
Sure. But I strongly dislike when my direct questions get answers that translate to "p...eel off". <span style="font-style: italic">As opposed to courteous attempts to explain (and so far few found me incapable of understanding and grasping the subject quickly
smile.gif
).</span>

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">So, I'm happy with a ballistic program which does that. I don't care how it works, unless I plan to write one, and after retiring from a career of doing things like that, I wouldn't touch that with the proverbial ten-foot pole.</div></div>
Ah, but I cannot retire yet! (That must be it!!
grin.gif
) Ask me again after I do!
grin.gif


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I use all Macs myself and have one of my iMacs dual booted to Windows using bootcamp to run the Windows stuff. Then I just have an iPaq.</div></div>
All the Windows stuff I use - and Lord knows there isn't a lot of it - is run under VMware. No direct boot, and that VM gets deleted/purged/re-installed often. Related to my work. Yeah I contemplated iPaq back when - didn't get it in time, then things cooled off.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I like FFS because it's a chip not dependent on any program, you just insert, like i have a Trimble Nomad that I got on sale at USCAV, less than $1k, so it has all the features and I can simply pop a chip in an not have to back it up to anything.</div></div>
That is something to consider - compact and reasonably convenient. Thanks for pointing at this solution.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">But I keep a lot of it on hand because people ask and I want to be able to give reliable answers.</div></div>
grin.gif
I hear you! Luckily people aren't coming to <span style="text-decoration: underline">me</span> for those kinds of answers, so I just suit myself with the gear I assemble (almost misspoke to say "collect"
wink.gif
).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Gus is working on a Window 7 Phone program that is supposed to have more horsepower than the PDAs.</div></div>
Well, to be blunt - I don't like Gus's associates, suspect they follow the policy that he set; and until I forget all about that exchange with Patagonia (<span style="font-style: italic">or unless I <span style="text-decoration: underline">really</span> <span style="text-decoration: underline">need</span> his LB3 - which doesn't sound likely</span>) I'll treat P.B. as an infected file. So he can take his Win 7 Phone and do with it as he pleases.
grin.gif


Now there's always QL/QTU if I ever need to go that route.

I have a couple of software pieces at work that require Windows 7 and am not crazy about them of Win 7 itself (though I admit it's not as unusable as Vista), and have neither need nor desire whatsoever for a Windows 7 Mobile device. <span style="font-style: italic">When I need horsepower - quad-core i7 Mac usually delivers, and if I need more - there's computing cloud at work, <span style="text-decoration: underline">really</span> more than enough for most of my needs - unless I get rabies and decide to compute global weather!
grin.gif
</span>

Tracking back some:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sharac</div><div class="ubbcode-body">]To me you are a statistician (i'll compute, i'll estimate or i'll do a voodoo magic whatever it takes to get a result) and Bryan is a mathematician (i'll rather die than take a guess and no result is better than result based on "guess"). There has been a long history of conflict between those two branches and you two won't solve a thing in this area . While mathematicians allow for no error no matter what statisticians will accept a predetermined amount of error and get some usable solution.</div></div>
No offense meant - but the above reveals lack of understanding of what statistics (as a field of mathematics) is or does.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sharac</div><div class="ubbcode-body">...however fact also is that G7 is NOT the standard...</div></div>
This is 100% <span style="text-decoration: underline">wrong</span>. G7 absolutely is a standard, along with G1, G2, etc. What you probably meant to say is "G7 is not a standard that the bullet-making industry embraced widely today".
 
#70
Re: G1, G7 Ballistics Coeficient?

That is what i meant yes. As Bryan (as i see it) is trying to push the makers/users to adopt G7 as a standard upon which modern bullets are marketed and trajectories computed...

As for statistics/mathematics i may have chosen a poor wording but me being around both there definitely is "bad blood" between them especially if talking to older mathematics professors who view statistics as an ugly duckling. As i'm from IT field i couldn't care less about it i just find it interesting in this context. I tried to illustrate differences in opinion as to what is "close enough and works" vs "not optimal, needs tweaking not precise" - thats all.
 
#71
Re: G1, G7 Ballistics Coeficient?

Mouse,

To be fair and provide some context, you're the only one I've ever heard of having a negative customer support experience with Gus. He's well known for his timely and thorough responses. Not questioning your word, just letting you know that's not how he usually is.

-Bryan
 
#72
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">Mouse,

To be fair and provide some context, you're the only one I've ever heard of having a negative customer support experience with Gus. He's well known for his timely and thorough responses. Not questioning your word, just letting you know that's not how he usually is.</div></div>
Don't know and can't say about Gus personally - as his employees did a 100% successful job of screening him from my emails. So he never gave me a chance to find out how responsive he is.

I've sent two requests (one through their Web site, and one directly) with questions. Here are the responses (sensitive/military IDs removed):

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1st email from Patagonia</div><div class="ubbcode-body">
Dear Sir,



Please check the following link for some comparison of our software against real Doppler data.



http://www.longrangehunting.com/articles/ballistics-predictions-3.php



Unfortunately we don’t have at hand any other specific documentation on the details of the ballistics engine, other than the website.



Please let me know if we can be of further help.



Best regards,



PB</div></div>


and

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 2nd email from Patagonia</div><div class="ubbcode-body">
Dear Sir,



Since he is not available for answering your questions, let me try to address some.



The program has no any Doppler data built-in, the article just shows a comparison to actual Doppler downrange data, as provided by other source.



The program does not need any Doppler input at all.



To define the input data and creating a custom drag curve, the program uses the BC and DC values.



Best regards,



PB



From: ........................gov>
Sent: Tuesday, February 22, 2011 2:45 PM
To: [email protected]
Subject: Fwd: Questions on details of LB3 program



PB, if you get this message - please make sure that Gus sees it. I've already seen your reply and am not happy with it. I wish to continue this conversation with Gus rather than with you.

-------- Original Message --------

Subject:


Questions on details of LB3 program

Date:


Tue, 22 Feb 2011 12:41:05 -0500

From:


..................gov>

Reply-To:


...........gov

Organization:

................

To:


[email protected]



Gus,



Could you please answer the following questions, that I got trying to

understand your program and its advantages, and to determine how it

relates to other programs on the market?



1. For what bullets (particularly in 308 Win and 338 LM) does your

program use Doppler radar data?



2. How - i.e. based on what - does your engine create the direct

(Mach-based) drag curve for a given projectile (considering that each

individual projectile would be different - and thus have a different

drag curve)?



3. As your program appears to use direct computation (closed-form

solution) rather than relate to differences from the standard projectile

- why (and what for) does your program need G1 BC (and/or G7 BC) which

basically tells how the given bullet is more (or less) aerodynamic than

the standard Type 1 (or Type 7) projectile (that in my understanding is

only used/useful in Point Mass approach)?



Thank you!</div></div>
 
#73
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan</div><div class="ubbcode-body">Pejsa's equations aren't covered in McCoy. You have to get Pejsa's book.</div></div>
Thank you! Yes I'll look up the references (our library most likely has them).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">It looks simple at first (like only having one set of closed equations to apply). But then you find out you need a whole different set for transonic, another for subsonic, each with their own bullet performance metrics, it's a quagmire. Then you find that the BC you're giving it isn't really a BC, but instead is... something else. Then there's the DK; just come up with that... somehow, for each bullet, or just use the same one for all bullets, whatever you feel like doing to give the program a little bit of personality.

If you really want a headache, just get his book and read it. Then you can code you're very own, unique, one of a kind ballistics program!</div></div>
grin.gif
Actually, while it <span style="text-decoration: underline">should be</span> simple enough to code <span style="text-decoration: underline">an implementation</span> (just to create an example of an e.g. Pejsa solver), to make it (a) accurate enough to be useful, and (b) comparable with such a standard as e.g. Bullet Flight sets - would require efforts and <span style="text-decoration: underline">time</span> which I just can't see myself investing in the reasonable future. As for the headache - thanks, my recently-past cold provided me with the right amount, no need for more just yet.
smile.gif


Though I could see how being an author of a unique one of a kind ballistics program can entice a person.
grin.gif


<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">And when you get tired of tweaking it for each and every bullet you shoot, you can just go back to what everyone agrees is the 'best possible' solution: standard G7 BC's and a point mass sovler.</div></div>
grin.gif


Actually I'm thinking that current desktop computers should have enough horsepower to run a 6-DOF model, and be able to produce a decent numeric solution. Why in your opinion application developers don't do that? Particularly those that make desktop applications (rather than PDA etc)?
 
#74
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Actually I'm thinking that current desktop computers should have enough horsepower to run a 6-DOF model, and be able to produce a decent numeric solution. Why in your opinion application developers don't do that? Particularly those that make desktop applications (rather than PDA etc)?</div></div>

I wouldn't speculate on the motivation of others, but what I do know is that you only need a basic high school level grasp of algebra and MS Excel in order to code Pejsa's supersonic equations. In 15 minutes, you could have a simple spreadsheet that gives you drop, tof, velocity, etc for the supersonic range of a bullets flight which is sort of close to the output of a 'real' program. Now if you want to model trajectories below 1200 fps, the complexity increases dramatically. Then if you want to model temperature effects on mach number (Pejsa equations are based in velocity, not Mach), then there's another patch, etc, etc.

So to answer your question, I would guess that pejsas equations appeal to people because they can be coded pretty quick and easy which enables those without knowledge of numeric methods to create a ballistics solver, and move on to the interface, libraries, features, etc. I don't think anyone perceives modern processors to be incapable of numerically solving the equations, rather it's modern humans not capable of coding the numerical solutions (no offence intended toward modern humans).

Having said that, if you have a unique application that is resource limited, like if you wanted a ballistics program on a watch, or in a LRF, or some other device a low performance processor, the numeric solution might be too slow. In that case, Pejsa's equations might be the ticket because they enable an approximation where the numeric solution is just too computationally intensive to be viable. But there's no doubt that modern PDA's and phones have more than enough processing power to solve the equations numerically so there's no reason to use approximations on them.

-Bryan
 
#75
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">....current desktop computers should have enough horsepower to run a 6-DOF model, and be able to produce a decent numeric solution......</div></div>
......I don't think anyone perceives modern processors to be incapable of numerically solving the equations, rather it's modern humans not capable of coding the numerical solutions (no offence intended toward modern humans).</div></div>
grin.gif


I see. So in your opinion, the difficulty is not in finding/determining the appropriate drag coefficients etc. - but more likely just modern humans' aversion to coding a "man-size" (fairly complex) numeric solution?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Having said that, if you have a unique application that is resource limited, like if you wanted a ballistics program on a watch, or in a LRF, or some other device a low performance processor, the numeric solution might be too slow. In that case, Pejsa's equations might be the ticket because they enable an approximation where the numeric solution is just too computationally intensive to be viable. But there's no doubt that modern PDA's and phones have more than enough processing power to solve the equations numerically so there's no reason to use approximations on them.</div></div>
Yes I see. Makes sense.

Speaking of solutions - where does Point Mass (3-DOF as I understand?) fall complexity-wise? How much simpler - compared to 6DOF - are its equations, and the corresponding numeric solutions?
 
#76
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I have the complete email from Gus,

<span style="font-style: italic">Please find attached some new slides based on Doppler data for the .50BMG,
provided by the Spanish Army (now they are running LB3 with their SF forces,
and the Brits adopted it for ALL services and is now fully operational),
plus Lapua's own Doppler for the .338 LM</span>
</div></div>

Would like to clarify this: Is this guy saying that Brits have adopted LB3 for ALL services? Havent heard.
confused.gif


And Lapua published Doppler data for all bullets in all calibers, not only 338LM.
 
#77
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body">And Lapua published Doppler data for all bullets in all calibers, not only 338LM. </div></div>
JL,

A few (naive) questions for you. Where can I (if I can) get Lapua Doppler data, and what format is it in (i.e. what tools/software do I need to read it)?

And what do you mean by "for all bullets" - probably Lapua bullets only? Or did Lapua publish Doppler data for e.g. Sierra MatchKing? Where can I find the list of non-Lapua bullets that Lapua has Doppler data for?

Tnx!
 
#79
Re: G1, G7 Ballistics Coeficient?

I have to tweek the fps and the BC to get my JBM ballistics charts to match my real world dope too. One thing on tweeking. If you want to hold the short range MOA's where they are, and vary the long range MOA's, then change the BC.

If you want to change the short range MOA's and keep the long range MOA's where they are, then change the fps.

I hope I explained that in a way you can understang it. If makes sense if you think about it. BC makes more difference for long range becuase it represents the drag of the bullet. FPS changes the short range more because it's going faster at first. I think I am right here.
 
#80
Re: G1, G7 Ballistics Coeficient?

I think the whole point is that you shouldn't have needed the tweaking. For a load which you know the dope (and mind you if you're serious about shooting you SHOULD know your dope for loads you shoot with) you don't need any tweaking as you know the trajectory so tweaking comes into play when extending maximum range to get accurate prediction. For end user tweaking to occur you need to register/observe POI over several distances so why in the world would you go and play with ballistics program if you have drops for 100, 300, 600, 700m and than loose a lot of time tweaking to get 200 4/5/ as difference is such that sighters will be easily corrected (and remembered for future reference). Ok if you intend to shoot at 700+ to get on paper or have ballistics program adjust your dope for different conditions (height of a range, temperature etc...) but frankly if you train and shoot in known environment (sport shooting) a good practice is keeping your shots logged and having good personal shooting database.
 
#81
Re: G1, G7 Ballistics Coeficient?

I need to tweek the JBM Ballistics to get a ballistics table that matches my real world shooting. Then once I have that ballistics table I can use it to compensate for temperature and altitude variations (Density Altitude), which may be signifigant, causing more than 1 moa difference at the longer ranges.

For bench rest shooting, since you allowed sighters, and it's just one distance per match, there really is no need for a ballistics table at all, just the moa you need at the distance you shoot.
 
#82
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I have the complete email from Gus,

<span style="font-style: italic">Please find attached some new slides based on Doppler data for the .50BMG,
provided by the Spanish Army (now they are running LB3 with their SF forces,
and the Brits adopted it for ALL services and is now fully operational),
</span>
</div></div>

Would like to clarify this: Is this guy saying that Brits have adopted LB3 for ALL services? Havent heard.
confused.gif

</div></div>

Again- can anybody from inside confirm this?

Its just that I happen to know LR/sniper related people closely involved to Brits as well as Spanish army- this I first time I heard LB3 mentioned. However- I have heard that Brits are using/testing other software, but that is not LB3.
 
#83
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: JL</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">I have the complete email from Gus,

<span style="font-style: italic">Please find attached some new slides based on Doppler data for the .50BMG,
provided by the Spanish Army (now they are running LB3 with their SF forces,
and the Brits adopted it for ALL services and is now fully operational),
</span>
</div></div>

Would like to clarify this: Is this guy saying that Brits have adopted LB3 for ALL services? Havent heard.
confused.gif

</div></div>

Again- can anybody from inside confirm this?

Its just that I happen to know LR/sniper related people closely involved to Brits as well as Spanish army- this I first time I heard LB3 mentioned. However- I have heard that Brits are using/testing other software, but that is not LB3.</div></div>

Email Gus,

All I have, is what is written, I never asked for clarification, however the slides were included, not that it says anything.

The source is better than second hand information which is what I gave you, although the email is from Gus.
 
#84
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Email Gus......</div></div>
Does Gus have some kind of publicly-known/published email? Or is JL "known" enough to be allowed "direct access" to the "big boss"? I wasn't able to reach Gus via email - only his employees.

Also, I suspect that when JL said "somebody from inside" he meant British Armed Forces rather than P.B. Of course I could be mistaken.
 
#85
Re: G1, G7 Ballistics Coeficient?

LL, I understand that You dont have any further info on this, and you just quoted email LB3 developer sent you as it was.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mouse07410</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">Email Gus......</div></div>
Does Gus have some kind of publicly-known/published email? Or is JL "known" enough to be allowed "direct access" to the "big boss"? I wasn't able to reach Gus via email - only his employees.

Also, I suspect that when JL said "somebody from inside" he meant British Armed Forces rather than P.B. Of course I could be mistaken. </div></div>
Yes, I particulary ment end user(s), not PB company.
Bit surprised about quoted email- since it said <span style="font-style: italic">"Brits adopted it for ALL services and is now fully operational".</span>
Still I havent heard about it- and had a chat with a certain Brit about (other) mobile softwares and possible field tests with army in GB not too long ago.
Its just funny he didnt mention about LB3, thats all.
But its still possible, not saying that.
 
#86
Re: G1, G7 Ballistics Coeficient?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lowlight</div><div class="ubbcode-body">We found one is not really better than the other, both give you roughly the same information and both require you to "tweak" the data to work.

However, you don't have to take my word for it, here is comparison conducted by someone else using Patagonia Loadbase 3 with real world Doppler, G1, & G7 as they compare to each other from 1000m to 1750, using the 338LM 250gr Scenar. This is raw data provided, neither the G1 or G7 numbers were adjusted to match, simply outputted as LB3 processes it.

Screen-shot-2011-02-10-at-12.18.13-PM.png

</div></div>

Old topic, but:

Been using Shooter a while since my mobile is android nowdays.
Did some Doppler/G7 comparsions as well using Quick Target ultimate as reference.

For some reason I wasnt able to tweak G7 to match radar data as well as that chart shows- less than click error up to 1600meters.

I wonder what is reason for this? Could it be that PB uses "tweaked" G7 as well?
For instance, with 250gr Lapua LockBase, I had to do two different bullet profiles in order to get max one click error: 0.307 BC up to 1100 meters, and 0.301 beyond that point. That way it matches up to 2000meters.
With 250 Scenars, BC 0.322 seemed to give less than click error up to 1400 meters but after that error is again bigger than in chart you attached.

Not a big deal or huge error- just wondering what causes difference.
MV 900 mps @ 15 celcius, ICAO std weather.
 
#87
Re: G1, G7 Ballistics Coeficient?

JL,

I personally find the data Lowlight quoted to be less than useful or conclusive. All it shows is that one can tweak/twist anything into anything given enough efforts. Which - as I suspect - was the main point in posting that quote. Oh, and I'm certain PB uses banded and "tweaked" G7 BC as well.

Not knowing Muzzle Velocity and zero/current atmospherics for that data - you can't scientifically validate it or duplicate the computations: matching one part of the trajectory you're just as likely to screw up another part. Too many unknowns.

But even for the closer-matching G7 it makes sense to use banded BC, especially for transonic region (I don't know where one would get them - the best available test data from Bryan Litz stops at about 1.3 Mach, when ideally I'd like to see it all the way down to say 0.7 Mach).
 
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