New Lapua 6DOF Ballistics Solver

[Berger.Fan222]

http://www.lapua.com/ballistics/

Anyone try it yet? Sure looks interesting. Seems that right now only Lapua bullets are fully supported, but with the Nammo/Berger merger, one hopes that Berger bullets may be supported soon. The dynamic/gyroscopic stability calculations seem particularly interesting.

 

[JPeelen]

To do a 6 degrees of freedom (6DOF) computation you need around 10 coefficients per bullet in addition to the custom drag model (drag coefficient). These are very difficult to measure even by a first class professional institution. And it costs a lot.
The problem is not so much in doing the computation but in the reliability of the bullet data. Is this data really measured or an informed guess? The advantages of a 6DOF computation can only show up if the data quality problem is solved.
It will take a lot of time to build an opinion on this new Lapua software.

 

[Berger.Fan222]

To do a 6 degrees of freedom (6DOF) computation you need around 10 coefficients per bullet in addition to the custom drag model (drag coefficient). These are very difficult to measure even by a first class professional institution. And it costs a lot.
The problem is not so much in doing the computation but in the reliability of the bullet data. Is this data really measured or an informed guess? The advantages of a 6DOF computation can only show up if the data quality problem is solved.
It will take a lot of time to build an opinion on this new Lapua software.

This presentation explains how the coefficients may be determined:

http://www.dtic.mil/ndia/2012armaments/Wednesday13615siewert.pdf

 

[kombayotch]

I tried it. In imperial mode, it was nearly 2x off (12.4 mils vs. 6.9 mils). You have to enter the bullet weight in grams in spite of being in imperial mode. inHg jumps in full inches in the HUD. Outputs are displayed in clicks and inches instead of mils or MOA. I enter 3100 fps for MV, but the solution tables show 2625 fps. MV. There are probably other issues, but that is as far as I got.

I'm using the Android version. Maybe the iOS one is better...

 

[Berger.Fan222]

I tried it. In imperial mode, it was nearly 2x off (12.4 mils vs. 6.9 mils). You have to enter the bullet weight in grams in spite of being in imperial mode. inHg jumps in full inches in the HUD. Outputs are displayed in clicks and inches instead of mils or MOA. I enter 3100 fps for MV, but the solution tables show 2625 fps. MV. There are probably other issues, but that is as far as I got.

I'm using the Android version. Maybe the iOS one is better...

Aah, early version has lots of bugs. Not ready for prime time in the US. Thanks for the report. I hope you make a report to Lapua also, so they can start working on it.

Maybe now that they (Nammo) have acquired Berger, they can get more American eyes on it and get those bugs worked out.

 

[kombayotch]

Got it at least giving a decent result now. You HAVE to set up the powder dv/dt with a custom bullet otherwise it uses a default of 2625 fps. for your MV instead of the value you put in the main configuration panel. More fields appear when you enable Powder dv/dt and one is V0 with a default of 2625.

 

[mac86951]

Also had to manually go into setup for units; tables still give inches, but moa shown elsewhere.

 

[B Mize]

I downloaded it, played with it for an afternoon.
Decided it was way to complicated for my simple mind. Deleted it from my phone.
I'll stick with shooter.

 

[eric32]

I did the same, too european for me.

 

[Capt. Oblivious]

I tried it. In imperial mode, it was nearly 2x off (12.4 mils vs. 6.9 mils). You have to enter the bullet weight in grams in spite of being in imperial mode. inHg jumps in full inches in the HUD. Outputs are displayed in clicks and inches instead of mils or MOA. I enter 3100 fps for MV, but the solution tables show 2625 fps. MV. There are probably other issues, but that is as far as I got.

I'm using the Android version. Maybe the iOS one is better...

Played with it for a couple hours yesterday and had the same problems. For now ill stick with my trusted app

 

[Travelor]

Here is a link to the 28 page instructions for use:

http://www.lapua.com/upload/ballistics/lapua-ballistics-app-user-info.pdf

 

[Berger.Fan222]

Here is a link to the 28 page instructions for use:

http://www.lapua.com/upload/ballistics/lapua-ballistics-app-user-info.pdf

Thanks for the link. One of the big challenges in designing or using a phone-sized app is the the interface. I tend to prefer computer programs like JBM where the screen is a lot bigger and my old eyes can find everything.

It'll be nice when someone releases a 6 DOF solver that will run on a full sized computer screen with custom drag curves and the whole 9 yards.

 

[DocUSMCRetired]

Thanks for the link. One of the big challenges in designing or using a phone-sized app is the the interface. I tend to prefer computer programs like JBM where the screen is a lot bigger and my old eyes can find everything.

It'll be nice when someone releases a 6 DOF solver that will run on a full sized computer screen with custom drag curves and the whole 9 yards.

The real problem is how do you get all the measurements needed to properly use 6DOF. Do you estimate them using other software or does the user have to measure them all?

 

[Berger.Fan222]

The real problem is how do you get all the measurements needed to properly use 6DOF. Do you estimate them using other software or does the user have to measure them all?

There's no way for users to measure them, but it would not be outrageous for a bullet manufacturer like Lapua to determine them accurately for their own bullets.

 

[mensajd]

Updated iOS app v1.0.1 is available. Some bug fixes including the V0 issue, but ft-lb energy calculations are way off.

 

[mensajd]

Updated iOS app v1.0.1 is available. Some bug fixes including the V0 issue, but ft-lb energy calculations are way off.

Subtle interaction in weight vs mass. Each gr (force) is 1/7,000 lbs (force). Acceleration of gravity is about g = 32.174049 ft/sec^2. Hence k = 1/(7,000 * 32.174049) if we use bullet weight in grains as a proxy for mass m in our kinetic energy formula.

So given my example bullet weight, in this case a 52 gr Berger FB match bullet at 3250 fps, (1/2)kmv^2 = 1,219.37 ft-lbs which is about right. Using the same bullet parameters, the Lapua app gives the erroneous result of 19 ft-lbs, which is WAY wrong. Please fix. Or PM me and I can fix it. No charge...

 

[DocUSMCRetired]

There's no way for users to measure them, but it would not be outrageous for a bullet manufacturer like Lapua to determine them accurately for their own bullets.

That's where running these kinds of apps becomes interesting. Do we have access to this kind of data? Yes we do. But the fun thing is finding a balance. Some users are going to want to be able to input their own data, and not use a library. Which is really not feasible in some instances. The whole 9 yards, so to speak, is an interesting balancing act. That can also require some teaching, but also explaining as to why you could have a CDM for a bullet, but not give the user the ability for self inputs.

None the less, it will be interesting to see how things progress.

 

[mensajd]

iOS v1.0.2 is available now. This version seems up to FCS standards in that basic functionality in imperial units seems to be working.