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Quest for g7 ballistics programs (can we please make a list)

 
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  #8  
Old 08-21-2009, 02:38 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

This is going to sound like I'm intentionally throwing rocks at a hornets nest, (i'm not)with that being said. If you use nightforce or any of the other software programs on the market to hit targets at 800,1000,1200 or further what difference does it make? If I can range a target at 1200 yrds put all the data into nightforce pull the trigger and hit that target why would I need G7?

BIGBUCK
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  #9  
Old 08-21-2009, 02:54 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

Quote:
Originally Posted by bigbuck View Post
This is going to sound like I'm intentionally throwing rocks at a hornets nest, (i'm not)with that being said. If you use nightforce or any of the other software programs on the market to hit targets at 800,1000,1200 or further what difference does it make? If I can range a target at 1200 yrds put all the data into nightforce pull the trigger and hit that target why would I need G7?

BIGBUCK

If you are truly doing that with the programs mentioned you are fudging something. Not trying to argue w/ you but I've used several programs enough to know that they aren't 100% w/o some fudging. There's a market (guys like me) for programs that use good data to come up w/ results. Again, not trying to be derogatory.
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  #10  
Old 08-21-2009, 03:45 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

Quote:
Originally Posted by bigbuck View Post
If I can range a target at 1200 yrds put all the data into nightforce pull the trigger and hit that target why would I need G7?
BIGBUCK
If you can git-r-done with single shots at every abstract range out to 1200, you got no problems in my view. But it is still relative...
For one, your capability must be taken to cold hard moa of accuracy(not grouping).
Second, can you really maintain this accuracy at any range?(again, not group shooting)
Most shooters can not.

A ballistic challenge for us relates to use of a poor standard in drag curve(G1). It's poor because it doesn't match ANY of our bullets. This mismatch causes our true G1 BC to vary with velocity, just as it varies with air density.
Normally, you enter a single G1 BC and your software must assume this is correct for your entered muzzle velocity.
Is it? Possibly for you, never for me..
Now as the fired bullet drops in velocity, it's real world G1BC departs from what you entered, and what your software assumes, because this is all based on the G1 drag curve,
I believe Bryan(Berger) has made efforts to help us reduce the real world affects of the 'G1 problem' by averaging G1 BC over a likely velocity range. There is potential here to cut error in half.

Another solution to the 'G1 problem' is to switch to a 'G7 problem'. This curve more closely matches that of long range bullets we use. It ain't perfect, never will be, but a step in the right direction. If your software could reference a truly matching curve for each iteration downrange, your BC would be right on the money and it would not change at all.

With this, your accuracy might drop off with distance in a very predictable manner, instead of seemingly abstract.
For instance, if you set a 1moa target at each 100yd increment out to 1200, and fire single shots to center of mark, you might expect that 1/4moa of accuracy at 100 would turn into 1/2moa at 500, and 3/4moa at 1000, etc. It gets tougher and tougher.
But using G1 BC, you might find that 1/4moa at 100 turns into 2moa at 1000, or just opposite(depending on where you zero'd).
I'm not talking about moa of grouping here. I'm talking moa of accuracy.

This is where all the interest in use of G7 comes from.

Last edited by Mikecr; 08-21-2009 at 03:49 PM.
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  #11  
Old 08-21-2009, 03:57 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

Quote:
Originally Posted by Mikecr View Post
If you can git-r-done with single shots at every abstract range out to 1200, you got no problems in my view.
This is where all the interest in use of G7 comes from.
Yup. Some good rationale explained here.
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  #12  
Old 08-21-2009, 05:20 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

Great discussion!

First I'd like to thank those who've set me straight on the G7 capable software; turns out LoadBase doesn't accept G7 BC's as I thought it did. It's been removed from the list.

I sure wish I was a smarter programmer and had the time, there's a real strong market for G7 capable PDA's. Right now, if you don't have an iPhone, it seems there aren't any options.

Lou,

You bring up a good point about computational resources, and the possibility of using unique drag curves for each bullet. Computers certainly aren't preventing us from doing that, but I think there are still other very practical and useful reasons to continue the use of BC's.

First, BC contains more than just drag information. It includes sectional density, and is an important 'comparison' number to use.

Second, there isn't enough experimental data to start using it exclusively. If you use
McDrag or some other computer prediction program, you're looking at +/- 10% error and it's no better than an estimated G1 BC.

My experimental data is collected using acoustic sensors, which means they only work (well) during the supersonic portion of the bullets flight. Using a BC referenced to a standard projectile, you can extrapolate the measured, high speed data down to transonic and subsonic speeds. You can also extrapolate to higher speeds than those tested because the standard curve is known. If you rely only on measured data, you can only predict trajectories over speed ranges that you've actually measured and that is a practical limitation.

When radar data exists, it's usually quite good and can be used to calculate very accurate trajectories. However, it's unlikely that such data will exist in bulk any time soon for anyone other than Lapua.

If you look at trajectories predicted with Lapua's direct drag data compared to a G7 BC that's based on the drag data, there is very little difference between the two trajectories at all ranges. There's certainly much less difference than a G1 vs G7 based trajectory.

I like to think of the move to G7 BCs as an important and practical improvement in the potential accuracy of ballistic calculations. Is it the most precise way? No. But it's the point of diminishing returns between complexity and accuracy. In other words, going to G7 BC's removes 90% to 95% of the velocity dependence problems associated with G1's, and most hunters/shooters can adopt the G7 BC's with little pain and confusion (provided the mobile software becomes available). Getting that last 5% to 10% would require using many other standards (G2, G5, etc...) or raw drag data unique to each bullet. There's no reason for some curious individuals not to explore these more complex options for their own use, but I don't feel they're the right solution for general use. Of course, that is a matter of my opinion, and is arguable.

I need to get on the ball and learn how to program PDA's already!

-Bryan
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  #13  
Old 08-21-2009, 05:41 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

Guys:

I contacted Gus this morning and in a couple of emails he has supplied some very interesting news. He said it was o.k. to share the correspondence so here goes.

I sent him an email and asked him about any future plans for LB to utilize the G7 drag form and I told him that most serious long range shooters considered it the way to go. Here is his reply.................

================================================== ========

Hi Dick,

Let me start by saying that LB3D is almost ready to roll. Just need to
finish some new features, since it's not a revamped LB2, it's a complete
rework, making it a 100% .Net-based app (same as LB3M), which entitled a LOT
of programming work, including some new features.

I've been busy developing and delivering the new ballistics system to be
fielded by the British Army Sniper Teams, and that took some time off LB3D.

On the other hand, LB3M next update is almost ready too, which incorporates
some changes to make it fully compatible (features and functions) with LB3D.

A new and novel method to account for MV/Air Temp compensation has been
developed (to fit the British requirement...lots of math there!) and will
make its way into LB3D/M.

Both, will do exactly what you've asked for. To give the user the option to
choose between G1/G7, among other things.

So, as you pointed out, no further need to use the Analyzer.

In fact, I've been discussing that with Bryan some time ago (he already
posted that LB is one of a few to handle G7), then I decided to make life
easier for those believers in G7...

Just let me point out, that LB3 ballistics engine does not rely on any "G"
function at all, however to make things simpler it uses a known BC (G1 or G7
now) as a "starting point".

I prefer not to go into the debate of G1 vs G7. But just let me say that G7
is neither new nor the Holy Grail. It's just a good form-factor to same
bullets, while bad to others.

Hope this make the wait worth!

Gus

================================================== ==============

I then replied that I knew the G7 was not the end all of ballistic problems but I felt that it would be a more accurate place to start than with G1.

Here is his reply...............

================================================== =============

Dick,

Well, improving the software is always a high priority, especially to listen to userís feedback, itís important to make the end user into the development cycle. I think the user deserves the best I can possible deliver.

Please go ahead and share the news.

The issue I see with G7 is not only its scarcity but the fact that itís not a good form-factor for almost any bullet shape. G1 on the other hand is a quite good compromise if handled adequately.

Of course and IMHO, G1/G7 is not the real answer to the problem of finding the best way to compute a bulletís deceleration, thatís why a Coefficient of Drag is always the best possible mathematical description.

However one must account for practicality, meaning the availability of those values, usually obtained by Doppler radar readings, which is so far the most accurate instrument to measure velocity loss, among other parameters.

Would you like to participate in Beta testing of LB3M/D ?

As such, youíll have the opportunity to test the software, suggest changes, etc

Thanks!

Gus

==============================================

I thanked him and told him I'd love to test it and also told him that I thought that Bryan would be an invaluable person to have evaluate the software.

We'll see how thing go but it sounds like Gus is continuing to do what he always has and that is to improve LoadBase and try to give us the best software out there.
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  #14  
Old 08-21-2009, 06:28 PM
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Re: Quest for g7 ballistics programs (can we please make a list)

Quote:
Originally Posted by ss7mm View Post
Guys:

I contacted Gus this morning and in a couple of emails he has supplied some very interesting news. He said it was o.k. to share the correspondence so here goes.
Hot diggity! Thanks for sharing this information. I really look forward to receiving the LB3 Desktop and being able to input Bryan's G7 drag function BCs for my Berger VLDs. This should result in a sweet fit of predicted drops to actual field drops right from the get-go. Life is about to get better.
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