Labrabaco: a G7 BC calculator from Labradar tracks

[FromMyColdDeadHand]

Wow, really interesting.

Specifically talking about 22lr subs, 1040fps, 40gr. There is a move towards higher twist barrels- and it is beyond me, but I thought that the twist would/could affect the BC. We are looking for 200yards+. To me at least, at about 175yards a beast comes and starts to flick those rounds. I think by the stability calcs, the 1x16 is too slow theoretically. Maybe for shorter and supersonic it works fine. I just have anecdotal differences right now, but it seems the 1x9 holds better groups At 200.

Also, if i set up one of those optical velocity readers at a longer distance, like 100 or 150 yards, Would that help?

I was just looking to find a BC to put into ballistic calc. The effect of the twist was just an interesting question.

What are the units that the labadar should be run? Feet or meters distance/speed?

 

[ptosis]

re: precision of 16" vs. 9" rifling – honestly I could not detect any significant difference. I mostly shoot the subsonic 40 gr ammo (to avoid the unpredictable transonic), and up to 500 m different good .22 rifles shoot pretty much the same. In terms of precision, different rifles seem to prefer different bullets (yet they all seem to agree on the bloody expensive Lapua), but I am not sure I am a good enough shot to really make a qualified statement.

re: another chrono at a longer distance – that is how I used to obtain and verify BCs in the past (quite successfully, albeit tediously). A magnetospeed under the barrel, and another velocity value at a known distance = the recipe for success. It is slightly less accurate than velocity decrease with time of flight, but largely good enough for all practical applications.

Problem is: sooner or later the far chrono dies by bullet wound. The only exception is the Steinert SuperChrono, which you can put behind something bulletproof, but it is extremely finicky to set up correctly (because it is extremely sensitive to angles of sight and of trajectory). Another possible solution is the shotmarker (cf. "one shot ST"’s experiments higher in this thread), which I personally did not test, but I am not hearing particularly convincing things about the velocity measurements precision.

The only reason why I started coding this whole Labrabaco thing is because of simplicity and reliability – you point the device to the target, you make sure your barrel is at the right distance from the radar box, and you simply shoot. And BC comes out of it.

re: units of measurement – it really does not matter (as long as distance is not measured in feet, which I did not properly test, because I cannot think in these weird units). Velocity in fps or in m/s, distance in m or in yd, the rounding errors are quite insignificant.

re: "just looking to find a BC to put into ballistic calc" – if you are talking specifically about .22 LR, you should perhaps wait for the next release. The G7 model is definitely not the way to go for round nose lead projectiles typically used in this calibre. The drag profiles, especially in the trans- and subsonic where the interesting .22LR stuff happens, are totally not the same. I have found some reasonably accurate Cd tables for the RA4 model (which is specifically tailored for typical .22LR ammo), and ordered a couple of bricks of [bloody expensive] Lapua ammo, which has the advantage of perfectly known trajectory. The next version will produce also RA4 BCs, which should address your (and mine) rimfire concerns way better than G7.

 

[ptosis]

v.0.8 is out, now with the taste of RA4, G1, and, while I was at it, G8.
(The default is still G7.)

Still at the same place: https://bc.geladen.ch/labrabaco/labrabaco.html

All you ever wanted to know about long-range ballistics of your rimfire trainer...

JBM and Strelok Pro (probably some others too) understand RA4 BCs.
Coming soon to Plan 33 (alas, not for the metric-impared).

Caveat: I did not test RA4 model results very extensively; would very much appreciate any feedback, especially from those who use Lapua ammo.

Enjoy.

 

[6.5SH]

v.0.8 is out, now with the taste of RA4, G1, and, while I was at it, G8.
(The default is still G7.)

Still at the same place: https://bc.geladen.ch/labrabaco/labrabaco.html

All you ever wanted to know about long-range ballistics of your rimfire trainer...

JBM and Strelok Pro (probably some others too) understand RA4 BCs.
Coming soon to Plan 33 (alas, not for the metric-impared).

Caveat: I did not test RA4 model results very extensively; would very much appreciate any feedback, especially from those who use Lapua ammo.

Enjoy.

Very nice!

With a 100 shot session of SK Standard Plus, 96 out of 100 valid tracks with the default filtering options.
Results for G1:
BC standard deviation: 0.011974951571587884
Average BC = 0.1302057202657062
SK's published G1 BC is 0.132

 

[ptosis]

Very nice!

With a 100 shot session of SK Standard Plus, 96 out of 100 valid tracks with the default filtering options.
Results for G1:
BC standard deviation: 0.011974951571587884
Average BC = 0.1302057202657062
SK's published G1 BC is 0.132

Cool! That is very close to the manufacturer's data, and certainly close enough for all practical applications.

Did you have a chance to shoot longer distances (e.g. 300+ m/yd) with this cartridge? How does the trajectory compare to the BC numbers?

 

[6.5SH]

Only on steel that I can't physically access. Using the SK stated value of .132 Strelok has been on to 400, at 512 impact was 1 full mil low IIRC.

 

[one shot ST]

Some screenshot about some test, LS 136 BC one match perfectly other very close to published BC, other are for SK LR same considerations

 

[ptosis]

Only on steel that I can't physically access. Using the SK stated value of .132 Strelok has been on to 400, at 512 impact was 1 full mil low IIRC.

re: 512 -- I am very curious whether the RA4 model gives more accurate predictions than G1 ?
Would you mind checking it, by setting RA4 model in Labrabaco, and feeding it the same Labradar data. Then we could see if the resulting BC, introduced in JBM or Strelok Pro with RA4 model, better fits the observed dope?

 

[6.5SH]

re: 512 -- I am very curious whether the RA4 model gives more accurate predictions than G1 ?
Would you mind checking it, by setting RA4 model in Labrabaco, and feeding it the same Labradar data. Then we could see if the resulting BC, introduced in JBM or Strelok Pro with RA4 model, better fits the observed dope?

RA4 gives:
BC standard deviation: 0.005967208339059481
Average BC = 0.10735645494962978

The 512 yard prediction adds another 0.8 mils of drop so in the ball park. Will have to try it and see how the closer distances line up.

ETA:
100 & 200 show the same numbers, 300 yards adds another 0.2 mils. I will have to make a trip to a local range that has 300 yard paper to get an actual measurement.

 

[ptosis]

Some screenshot about some test, LS 136 BC one match perfectly other very close to published BC, other are for SK LR same considerations

Sweet, thank you.

I must say I am pretty glad of the results that can be obtained.
(Of course, Labrabaco is by far not as accurate as industrial radars over longer distances, but for some manufacturers (did someone say Norma? Ruag?) that can be an easy fix, and a good starting point.)

 

[ptosis]

RA4 gives:
BC standard deviation: 0.005967208339059481
Average BC = 0.10735645494962978

The 512 yard prediction adds another 0.8 mils of drop so in the ball park. Will have to try it and see how the closer distances line up.

ETA:
100 & 200 show the same numbers, 300 yards adds another 0.2 mils. I will have to make a trip to a local range that has 300 yard paper to get an actual measurement.

Thanks!

On my side, I no longer have access to anything beyond 300m until March-April, when snow melts off the roads that lead to the mountain ranges. But I will run a few tests at 300, and also do some "armchair ballistics", to see how RA4 BCs compare to Lapua's Cd trajectories; will share it here.

 

[one shot ST]

yesterday, same rifle, same bullet same conditions, 4 different loads, published BC .288

 

[ptosis]

yesterday, same rifle, same bullet same conditions, 4 different loads, published BC .288

That gives an average of 0.2856978, which fits the manufacturer's data to 0.8%

Sweet! What kind of cartridge it is? And, by the way, do you run a EU-castrated Labradar, or a full-power Canada/US version?

 

[one shot ST]

That gives an average of 0.2856978, which fits the manufacturer's data to 0.8%

Sweet! What kind of cartridge it is? And, by the way, do you run a EU-castrated Labradar, or a full-power Canada/US version?

Lapua Scenar 136 L full power

 

[category_theory]

Hey all, So I posted another thread and someone pointed me to this thread... Not sure if folks are aware but the NEW FW True Ballistics Chronograph has the ability to calculate speeds at 4 and 5 different ranges that you can set in the chronograph. it then calculates a "simple BC" for you based on the environmental it grabs from your phone, the bullet mass you enter and the speeds it grabs.

My question is... how do I take the "simple BCs" and empirical data I am finding and back into a normalized BC (if that's a thing)....
Thanks y'all!

And if no one has gotten a FX true Ballistics Chrono yet holy hell it's amazing! up to 4500 ft/s and 5 speed calculations per flight and the battery lasts forever and the app is decent! And the stand is built into the unit! I get the appeal of the Garmin but shit man the FX is like WAY ahead of everything out there!

 

[MarshallDodge]

Smells like shill around here

 

[6.5SH]

Hey all, So I posted another thread and someone pointed me to this thread... Not sure if folks are aware but the NEW FW True Ballistics Chronograph has the ability to calculate speeds at 4 and 5 different ranges that you can set in the chronograph. it then calculates a "simple BC" for you based on the environmental it grabs from your phone, the bullet mass you enter and the speeds it grabs.

My question is... how do I take the "simple BCs" and empirical data I am finding and back into a normalized BC (if that's a thing)....
Thanks y'all!

And if no one has gotten a FX true Ballistics Chrono yet holy hell it's amazing! up to 4500 ft/s and 5 speed calculations per flight and the battery lasts forever and the app is decent! And the stand is built into the unit! I get the appeal of the Garmin but shit man the FX is like WAY ahead of everything out there!

Does it give a raw CSV data file per shot like the LabRadar? If it provides equivalent data you should be able to format some files and see what the tool returns.

If confident in your math and coding skills you can view the source on his page, the main bits are the links at the very bottom. I'm not that good math wise to make use of it in that manner.

 

[category_theory]

Smells like shill around here

Ha no honestly Ive tried Lab Radars and its cool but a pain in the ass.. I have a magneto too and I like it but its a one trick pony... I am just a product designed and engineer and love good well thought out products. Im a fan and a nerd .

 

[category_theory]

Does it give a raw CSV data file per shot like the LabRadar? If it provides equivalent data you should be able to format some files and see what the tool returns.

If confident in your math and coding skills you can view the source on his page, the main bits are the links at the very bottom. I'm not that good math wise to make use of it in that manner.

It does but the BCs I have to pull from the app manually. I filed a bug with them and well see if it gets fixed. that said I can pull them and format them myself. As per my math and coding skills... I have advanced degrees in math and worked in Silicon Valley my whole life so I may be able to hack some shit . I have looked at the code specifically yet in the app that's referenced here but will take a look tonight! thanks!

 

[category_theory]

Does it give a raw CSV data file per shot like the LabRadar? If it provides equivalent data you should be able to format some files and see what the tool returns.

If confident in your math and coding skills you can view the source on his page, the main bits are the links at the very bottom. I'm not that good math wise to make use of it in that manner.

Where is the source code? Is it posted on Github anywhere?

 

[6.5SH]

I was coming at it more from labrabaco re-calculating the BC, it will also output the BC variation for a series. That can be used in your normalization efforts.

ETA:
Re source, just right click the page and view page source.

 

[category_theory]

I was coming at it more from labrabaco re-calculating the BC, it will also output the BC variation for a series. That can be used in your normalization efforts.

ETA:
Re source, just right click the page and view page source.

Ah.. javascript! I am a C, C++ Python Fortran guy.. this new web stuff.... kids!

 

[category_theory]

Ah.. javascript! I am a C, C++ Python Fortran guy.. this new web stuff.... kids!

Also for anyone who'd like the source code like myself its here too: https://geladen.ch/wp-content/uploads/2023/04/labrabaco-2021-11-25-v.0.8.zip

 

[ptosis]

Ah.. javascript! I am a C, C++ Python Fortran guy.. this new web stuff.... kids!

Aw yeah! C++ and Perl -- stuff that God hacked the universe together with.

I'm a 20th century man myself, and cordially hate this DOM/CSS/JS stuff -- oververbose, heavy, thoroughly inelegant, and crippled by design -- but nowadays it's about the only way to write something platform-independent.

(This said, all apologies to those who would dive into labrabaco code; it's an ugly eye-bleeding spaghetti mess.)
If you have any questions, feel free to give me a kick -- either here, or through geladen.ch contact page.

 

[ptosis]

Hey all, So I posted another thread and someone pointed me to this thread... Not sure if folks are aware but the NEW FW True Ballistics Chronograph has the ability to calculate speeds at 4 and 5 different ranges that you can set in the chronograph. it then calculates a "simple BC" for you based on the environmental it grabs from your phone, the bullet mass you enter and the speeds it grabs.

My question is... how do I take the "simple BCs" and empirical data I am finding and back into a normalized BC (if that's a thing)....
Thanks y'all!

And if no one has gotten a FX true Ballistics Chrono yet holy hell it's amazing! up to 4500 ft/s and 5 speed calculations per flight and the battery lasts forever and the app is decent! And the stand is built into the unit! I get the appeal of the Garmin but shit man the FX is like WAY ahead of everything out there!

If you manage to get actual measured data from the FX box -- please let me know; I'm very curious to see what can be done with it (how far it tracks common projectiles, what are the noise levels, etc.).

I did not have a chance to play with it yet (the box does not seem to be available on our side of the pond), but from what I gather from my North-American friends, the "FX true" guys are not very forthcoming about the radar's internals and software.

The "actually measured" vs. "displayed" is a very important distinction; for example in Labradar's CSV files, the only actually measured values are time and SNR. The speed is calculated -- adjusted for the distance between the beam and the barrel (the radar can only measure radial velocity), and the distance is a rather rough approximation (rounded to the nearest foot ?) and is totally useless for any calculations.

re: converting the "simple BC" (or whatever the "FX true" are calling them) into normalised BCs for standard atmosphere -- logically speaking, it should be as simple as multiplying the "simple" BC for a real atmosphere by the std/real ratio of air density.

 

[ptosis]

re: converting the "simple BC" (or whatever the "FX true" are calling them) into normalised BCs for standard atmosphere -- logically speaking, it should be as simple as multiplying the "simple" BC for a real atmosphere by the std/real ratio of air density.

Now that I think of it, there's also the temperature, that is -- speed of sound difference. In addition to the above, one would also need to multiply by the ratio of Cd of reference drag model (e.g. G7 Cd) for Mach number (real temperature) / Mach number (standard 15°C)

 

[category_theory]

Yes, it is possible. Yes, it does work.

I have put together some code to calculate G7 ballistic coefficients from Labradar tracks. The tool is available here: https://bc.geladen.ch/labrabaco/labrabaco.html

It all runs in your browser, there is nothing to install, and it's free and open source.

Some bits of additional info are here: https://geladen.ch/en/labrabaco-v-0-5-beta-is-out/
and here: https://geladen.ch/en/tips-to-set-up-labradar-for-the-most-awesomest-results/

My deepest gratitude goes to entoptics @ longrangehunting.com forums, who provided absolutely precious data for design and calibration of the algorithms.

That is what can be expected:

Bullet​	ref BC​	BC src​	valid tracks​	baco BC​	diff, %​
GP90 (Fass90)	0.166	CH armee	15	0.167	0.7%
GP11	0.274	CH armee	16	0.270	-1.4%
RUAG BALL 8.6	0.312	vendor [*]	7	0.316	1.1%
Lapua Scenar-L 7.62 155gr	0.230	vendor	16	0.230	0.1%
GP90 (SG-553-LB)	0.166	CH armee	14	0.166	-0.1%
Hornady ELDM 6.5 147gr	0.351	vendor	16	0.332	-5.4%
Berger EOL 6.5 156gr	0.347	vendor	4	0.352	1.3%
Hornady ELDM 5.56 73gr	0.200	vendor	5	0.206	3.0%
Hornady ELDM 6.5 147gr	0.351	vendor	5	0.337	-4.1%
Hornady ELDX 6.5 143gr	0.315	vendor	4	0.312	-1.0%
Hornady ELDX 7 175gr	0.347	vendor	19	0.353	1.6%
SMK 223 69gr	0.169	Litz [**]	10	0.167	-1.1%
Hornady ELDX 6.5 143gr	0.315	vendor	7	0.315	-0.1%
Hornady ELDX 7 175gr	0.347	vendor	22	0.351	1.2%

​

[*] from trajectory data
[**] Applied Ballistics For Long Range Shooting, 2nd ed.

“Ref BC” is a known good G7 BC from “BC src”. “Baco BC” lists the values calculated by labrabaco from radar tracks.

(Wish I had an adult-size Doppler radar to check if Hornady ELDM 6.5 147gr really behaves so differently from all other bullets tested.)

Gory details will follow in a separate article. In short, the software uses a 5th order polynomial regression weighted by SNR (absolute, not dB) on all data points for V(t), then runs an actual 3DOF ballistic engine in reverse to iterate to the best-fitting BC.

You're welcome.

This is rad! And I know old but is there any source materials you can share on your methods for the calculations? And deep math and simulation methods are fine! The more technical the better! Thanks!

 

[LastShot300]

This is rad! And I know old but is there any source materials you can share on your methods for the calculations? And deep math and simulation methods are fine! The more technical the better! Thanks!

Comparing Hornady's Doppler (a real pro radar) to whatever LabRadar says is ...well...close to absurd. So, those so called "differences" means nothing unless the distances are known, conditions, etc. (Wind is critical) You can apply whatever curve fitting algo you want, but in the best case, it's a just a statistical illusion given the data uncertainty.

 

[category_theory]

Comparing Hornady's Doppler (a real pro radar) to whatever LabRadar says is ...well...close to absurd. So, those so called "differences" means nothing unless the distances are known, conditions, etc. (Wind is critical) You can apply whatever curve fitting algo you want, but in the best case, it's a just a statistical illusion given the data uncertainty.

That fair. I was asking more to learn about modern methods and practices and theory. I don’t have a LR but I do have the new FX True Ballistics and it gives a “simplified BC” based on environmentals and various velocity measures at different distances (user selected).

 

[LastShot300]

That fair. I was asking more to learn about modern methods and practices and theory. I don’t have a LR but I do have the new FX True Ballistics and it gives a “simplified BC” based on environmentals and various velocity measures at different distances (user selected).

My suggestion is to read the paper "Accurate Measurements of Free Flight Drag Coefficients with Amateur Doppler Radar" by Michael Courtney, there is a good deal of technical aspects discussed. The math is non existent unfortunately.

https://arxiv.org/ftp/arxiv/papers/1608/1608.06500.pdf

 

[ptosis]

This is rad! And I know old but is there any source materials you can share on your methods for the calculations? And deep math and simulation methods are fine! The more technical the better! Thanks!

Sure!
The core of it is a 3DOF small arms ballistic engine, originating with McCoy's formulas, and loosely based on old open source JBM code (heavily modified and bugfixed, especially in atmosphere and Cd curves processing bits).
The main loop (cf. ebalengine.js) is numerical integration over distance, using Heum / improved Euler method (the code is decently commented, check it out).
Labrabaco is the reverse application of the engine – running it iteratively with subsequently reduced BC adjustment steps, until the calculated velocity matches experimental values.
Labradar output undergoes basic cleanup (cf. labrabacoengine.js) to reduce noise (eliminate data points least fitting a linear regression, cf. chopShop() function), and reject obviously erroneous tracks (e.g. neighbours' shots).
That's the essence of it, feel free to give me a kick if you have further questions.
BTW, a direct (rather than reverse) application of the engine is available here: https://bc.geladen.ch/plan33/plan33.html (caution: not for metric-impared)

 

[ptosis]

Comparing Hornady's Doppler (a real pro radar) to whatever LabRadar says is ...well...close to absurd. So, those so called "differences" means nothing unless the distances are known, conditions, etc. (Wind is critical) You can apply whatever curve fitting algo you want, but in the best case, it's a just a statistical illusion given the data uncertainty.

To start with, the purpose of the exercise is certainly not to compare data from 2 different radars with vastly different power outputs.

As for the rest, this is... hmm... an interesting opinion. Would you mind substantiating any of these strong claims?

 

[LastShot300]

To start with, the purpose of the exercise is certainly not to compare data from 2 different radars with vastly different power outputs.

As for the rest, this is... hmm... an interesting opinion. Would you mind substantiating any of these strong claims?

Not really "strong claims" just real world data and how this works. LabRadar is, if everything goes well, capable up to 200 yards (give or take, to take downrange readings, given angle, projectile size, etc.) Thus and among other things it's not realistic to derive a BC based on such short distances, which is good for nothing (except for having fun). Not even LabRadar promotes it's use for calculating BCs....enough said. So, making a table comparing BCs derived this way is simply a long stretch to say the least. Basically you are cheating yourself annd even more if some sort of curve fitting algo is applied to the data. Also don't forget about the SNR. The baseline is at least 700 meters or about, before transonic.

 

[ptosis]

Not really "strong claims" just real world data and how this works. LabRadar is, if everything goes well, capable up to 200 yards (give or take, to take downrange readings, given angle, projectile size, etc.) Thus and among other things it's not realistic to derive a BC based on such short distances, which is good for nothing (except for having fun). Not even LabRadar promotes it's use for calculating BCs....enough said. So, making a table comparing BCs derived this way is simply a long stretch to say the least. Basically you are cheating yourself annd even more if some sort of curve fitting algo is applied to the data. Also don't forget about the SNR. The baseline is at least 700 meters or about, before transonic.

Sorry, this hardly qualifies as substantiation.

re: "just real world data and how this works" – would you provide some "real world data" in support of your statements, or is it just a figure of speech?

re: "Thus and among other things it's not realistic to derive a BC based on such short distances" – who told you that, and was that claim somehow substantiated by hard facts ?

re: "good for nothing (except for having fun)", "enough said", "simply a long stretch to say the least" – these statements are emotions and opinions, and do not qualify as substantiation. Again, are there any hard facts in support of your emotions and opinions?

re: "curve fitting algo" – I am not sure you understand the definition of "curve fitting", even less so the Labrabaco process (which has nothing to do with curve fitting) described above.

re: "Also don't forget about the SNR" – please let me know what I should not forget about SNR (except that you have heard the term).

In summary: So far, I have the impression that you have no idea what you are talking about. Welcome to prove me wrong.

***

On a more constructive note (and for other audience) ---

Since I have published Labrabaco, I am getting dozens of feedback messages from across the World (a pleasure to see others appreciating my work), and in the vast majority of cases, the G7 BC values are within 2% (and more often within 1-1.5%) of the optimal value published by the manufacturer. I personally run Labrabaco for dozens of unknown projectiles for the guys at the range, and it gets them pretty damn close over the whole supersonic range. This is hard, real-world data.

I know of the limitations of the approach, and I know what, say, a 1km radar track can give, but considering the 2% max G7 BC error (use your favourite calc for your favourite calibre to get the drop difference at 1000+ yd), the precision is rather impressive, especially so for for a consumer-grade device.

Also, before Lapua.com site redesign circa 2016, they had a common table of BCs for all their projectiles. Here's the archive.org copy:

Products - Lapua

web.archive.org

Mind the footnote, quoted verbatim: "Ballistic coefficients are based on Doppler radar data and calculated by Quick Target Unlimited Lapua Edition from V0 to V100" (emphasis mine).
The exact same BC values are listed for Lapua bullets to date, feel free to check on the site.

Again: Lapua calculates official published BCs on velocity loss over the first 100 m of trajectory. That's what Lapua do. I have not heard a lot of complaints about Lapua ballistic data.

What's good enough for them is good enough for me. Real world data confirms it allright, and, in absence of a mil-grade Doppler radar, and in absence of non-bullshit arguments against the approach, I'll keep exploring what's available.

 

[LastShot300]

Sorry, this hardly qualifies as substantiation.

re: "just real world data and how this works" – would you provide some "real world data" in support of your statements, or is it just a figure of speech?

re: "Thus and among other things it's not realistic to derive a BC based on such short distances" – who told you that, and was that claim somehow substantiated by hard facts ?

re: "good for nothing (except for having fun)", "enough said", "simply a long stretch to say the least" – these statements are emotions and opinions, and do not qualify as substantiation. Again, are there any hard facts in support of your emotions and opinions?

re: "curve fitting algo" – I am not sure you understand the definition of "curve fitting", even less so the Labrabaco process (which has nothing to do with curve fitting) described above.

re: "Also don't forget about the SNR" – please let me know what I should not forget about SNR (except that you have heard the term).

In summary: So far, I have the impression that you have no idea what you are talking about. Welcome to prove me wrong.

***

On a more constructive note (and for other audience) ---

Since I have published Labrabaco, I am getting dozens of feedback messages from across the World (a pleasure to see others appreciating my work), and in the vast majority of cases, the G7 BC values are within 2% (and more often within 1-1.5%) of the optimal value published by the manufacturer. I personally run Labrabaco for dozens of unknown projectiles for the guys at the range, and it gets them pretty damn close over the whole supersonic range. This is hard, real-world data.

I know of the limitations of the approach, and I know what, say, a 1km radar track can give, but considering the 2% max G7 BC error (use your favourite calc for your favourite calibre to get the drop difference at 1000+ yd), the precision is rather impressive, especially so for for a consumer-grade device.

Also, before Lapua.com site redesign circa 2016, they had a common table of BCs for all their projectiles. Here's the archive.org copy:

Products - Lapua

web.archive.org

Mind the footnote, quoted verbatim: "Ballistic coefficients are based on Doppler radar data and calculated by Quick Target Unlimited Lapua Edition from V0 to V100" (emphasis mine).
The exact same BC values are listed for Lapua bullets to date, feel free to check on the site.

Again: Lapua calculates official published BCs on velocity loss over the first 100 m of trajectory. That's what Lapua do. I have not heard a lot of complaints about Lapua ballistic data.

What's good enough for them is good enough for me. Real world data confirms it allright, and, in absence of a mil-grade Doppler radar, and in absence of non-bullshit arguments against the approach, I'll keep exploring what's available.

Too long to answer...because you suffer the syndrome of "I'm always right, most especially when I'm wrong"

You know what's funny? You asserted my post forgetting I was replying to another post, then as usual, you "macho stamina" pops- up

1) Did I ever mentioned your software? NO.
2) Did I ever contested any claim you made before this post? NO.
3) What the heck has Lapua to do with this thread? NOTHING.
4) "I know the limitations of the approach"..(your words)..LOL and it's me speaking nonsense...c'mon...I expected better from you !

The rest of your bla-bla-bla is the usual meaningless wording just to say "I'm right"

Now...for the sake of NOT confusing the audience (except you, my bad LOL) :

1) Clearly you understand nothing by claiming that measuring downrange velocities up to the effective LabRadar ranges is "good"...please...tell me another joke...sorry, but you are making a fool of yourself with JUST that line. Trust me...
2) If you need to understand SNR in the context of the previous post...then you are a rookie and replying you is moot.
3) Emotions...really? What do you expect from a public forum? An answer 3 pages long? How old are you?
4) On curve fitting....you need text to take a course on reading comprehension... one more time...I wasn't addressing your post. Capisce?

5) "Again: Lapua calculates official published BCs on velocity loss over the first 100 m of trajectory." Really? Are you kidding us? And for that they need a pro Doppler radar?

6) "Ballistic coefficients are based on Doppler radar data and calculated by Quick Target Unlimited Lapua Edition from V0 to V100"...again you need urgently to take a lecture on reading comprehension

7) How many ELR shooters are actually using Lapua app or QTU? maybe 10?

Proving you right/wrong is a futile exercise in patience..not interested. Anyway, there is no need to...just read your own answers.

It's a pity your ego is way bigger than your actual knowledge of ballistics...how many people actually care and use your software? 10? maybe 15?

Keep going on because I cannot care less about you. Good luck my friend.

PS: take a good read on how-to Doppler-derived CDs procedures and best practices...you clearly need to expand your horizons beyond the internet. My serious advice is learn from the pros.

Here you go:

from Berger
"to shoot through a chronograph at 200 yards, but at that close of a distance, your measurement is highly subject to error."
"is all you need to properly characterize your bullet in a ballistics program for effective trajectory predictions out to the bullets transonic range (the range where the bullet has slowed to Mach 1.2, or about 1340 fps)."

Measuring BCs

Measuring Ballistic Coefficients (BCs) is one of those things that’s easy to do in principle, but very difficult to do accurately in practice. Remember, BC is most directly described as the ability of the bullet to retain velocity. So, the most direct way to measure BC is to measure the

bergerbullets.com

from Oehler:
"For the best results, the downrange target should be placed near the range at which the bullet velocity has decayed to approximately Mach 1.2 or 1350 feet per second."

from Hornady
"Most projectiles exhibited BC’s relatively close to published values for 150 to 200 yards of flight. Beyond these distances they all showed BC’s substantially below published values"

So, be my guest and keep measuring at 100 yards...

and some free advice...beware of the Wind...can make BCs differences of up to 11%

 

[ptosis]

Too long to answer...because you suffer the syndrome of "I'm always right, most especially when I'm wrong"

You know what's funny? You asserted my post forgetting I was replying to another post, then as usual, you "macho stamina" pops- up

1) Did I ever mentioned your software? NO.
2) Did I ever contested any claim you made before this post? NO.
3) What the heck has Lapua to do with this thread? NOTHING.
4) "I know the limitations of the approach"..(your words)..LOL and it's me speaking nonsense...c'mon...I expected better from you !

The rest of your bla-bla-bla is the usual meaningless wording just to say "I'm right"

Now...for the sake of NOT confusing the audience (except you, my bad LOL) :

1) Clearly you understand nothing by claiming that measuring downrange velocities up to the effective LabRadar ranges is "good"...please...tell me another joke...sorry, but you are making a fool of yourself with JUST that line. Trust me...
2) If you need to understand SNR in the context of the previous post...then you are a rookie and eplying you is moot.
3) Emotions...really? What do you expect from a public forum? An answer 3 pages long? How old are you?
4) On curve fitting....you need text to take a course on reading comprehension... one more time...I wasn't addressing your post. Cappice?

5) "Again: Lapua calculates official published BCs on velocity loss over the first 100 m of trajectory." Really? Are you kidding us? And for that they need a pro Doppler radar?

6) "Ballistic coefficients are based on Doppler radar data and calculated by Quick Target Unlimited Lapua Edition from V0 to V100"...again you need urgently to take a lecture on reading comprehension

7) How many ELR shooters are actually using Lapua app or QTU? maybe 10?

Proving you right/wrong is a futile exercise in patience..not interested. Anyway, there is no need to...just read your own answers.

It's a pity your ego is way bigger than your actual knowledge of ballistics...how many people actually care and use your software? 10? maybe 15?

Keep going on because I cannot care less about you. Good luck my friend.

PS: take a good read on how-to Doppler-derived CDs procedures and best practices...you clearly need to expand your horizons beyond the internet. My serious advice is learn from the pros.

Here you go:

from Berger
"to shoot through a chronograph at 200 yards, but at that close of a distance, your measurement is highly subject to error."
"is all you need to properly characterize your bullet in a ballistics program for effective trajectory predictions out to the bullets transonic range (the range where the bullet has slowed to Mach 1.2, or about 1340 fps)."

Measuring BCs

Measuring Ballistic Coefficients (BCs) is one of those things that’s easy to do in principle, but very difficult to do accurately in practice. Remember, BC is most directly described as the ability of the bullet to retain velocity. So, the most direct way to measure BC is to measure the

bergerbullets.com

And from Oehler:
For the bestresults, the downrange target should be placed near the range at which the bullet velocity has decayed to approximately Mach 1.2 or 1350 feetper second.

from Hornady
"Most projectiles exhibited BC’s relatively close to published values for 150 to 200 yards of flight. Beyond these distances theya ll showed BC’s substantially below published values"

So, be my guest and keep measuring at 100 yards...

and some free advice...beware of the Wind...can make BCs differences of up to 11%

SNR is unsatisfactory, try again.

I reiterate:
re: "just real world data and how this works" – would you provide some "real world data" in support of your statements, or is it just a figure of speech?

re: "Thus and among other things it's not realistic to derive a BC based on such short distances" – who told you that, and was that claim somehow substantiated by hard facts ?

re: "good for nothing (except for having fun)", "enough said", "simply a long stretch to say the least" – these statements are emotions and opinions, and do not qualify as substantiation. Again, are there any hard facts in support of your emotions and opinions?

re: "curve fitting algo" – I am not sure you understand the definition of "curve fitting", even less so the Labrabaco process (which has nothing to do with curve fitting) described above.

re: "Also don't forget about the SNR" – please let me know what I should not forget about SNR (except that you have heard the term).

 

[LastShot300]

SNR is unsatisfactory, try again.

I reiterate:
re: "just real world data and how this works" – would you provide some "real world data" in support of your statements, or is it just a figure of speech?

re: "Thus and among other things it's not realistic to derive a BC based on such short distances" – who told you that, and was that claim somehow substantiated by hard facts ?

re: "good for nothing (except for having fun)", "enough said", "simply a long stretch to say the least" – these statements are emotions and opinions, and do not qualify as substantiation. Again, are there any hard facts in support of your emotions and opinions?

re: "curve fitting algo" – I am not sure you understand the definition of "curve fitting", even less so the Labrabaco process (which has nothing to do with curve fitting) described above.

re: "Also don't forget about the SNR" – please let me know what I should not forget about SNR (except that you have heard the term).

Learn to read first...all addressed above.

 

[ptosis]

Learn to read first...all addressed above.

No. You have provided a fine example of flaming butthurt, which is not the same as real-world data and hard facts.

In the starting post and in a couple of contributions to this thread there is a number of real-world examples of successful usage of Labradar + Labrabaco to obtain G7 BCs, which are very close to optimal values, as advertised by reputable and reliable vendors.

This obviously does not replace a full-power mil-spec radar (which has the potential to provide complete and accurate Cd/Mach curves also covering transonic), but in most cases the approach is precise enough for practical purposes in the supersonic segment of the trajectory, within limits of the G7 model validity. This is reality.

You are saying that it's impossible, because you believe it's impossible, and if reality doesn't match your beliefs -- too bad for reality.

Beliefs are not about ballistics – they're about religion. I am not interested in religious debates, and would rather leave your reality denial issues to professionals.

You're wasting my time.

 

[LastShot300]

No. You have provided a fine example of flaming butthurt, which is not the same as real-world data and hard facts.

In the starting post and in a couple of contributions to this thread there is a number of real-world examples of successful usage of Labradar + Labrabaco to obtain G7 BCs, which are very close to optimal values, as advertised by reputable and reliable vendors.

This obviously does not replace a full-power mil-spec radar (which has the potential to provide complete and accurate Cd/Mach curves also covering transonic), but in most cases the approach is precise enough for practical purposes in the supersonic segment of the trajectory, within limits of the G7 model validity. This is reality.

You are saying that it's impossible, because you believe it's impossible, and if reality doesn't match your beliefs -- too bad for reality.

Beliefs are not about ballistics – they're about religion. I am not interested in religious debates, and would rather leave your reality denial issues to professionals.

You're wasting my time.

Yeah, sure! have you ever heard of something called COMMON SENSE? I know... may be shocking news to you

So what you are saying is akin to: the entire defense/munitions industry is basically led by a bunch of stupid professionals who may invest in a pro Doppler radar unit priced in the $500K range when some ignorant amateur can do exactly the same with a consumer grade $600 unit.

WOW! WOW! WOW!

You may be right...who in hell needs to measure downrange velocities up to 2000 when trajectory can be perfectly modeled by taking readings at 100? Really? Please tell me you are not supporting such statement.

OK..,if you are shooting inside 500 that may work...but in the real ELR world that won't cut the deal. Capisce?

Oh! My bad, you don't do ELR work! So what you may know about that?

Not to mention that you olimpically ignored what Berger, Oehler and Hornady has to say about measurement ranges...again...what a bunch of idiots, aren't they?

Whatever scientific fact that doesn't fit your narrative is simply dismissed. Old tactics but NOT effective.

For about 4 years I did contractor work for the Army, running a Weibel SL-30031P unit ....should I heard you before, our work would have been a lot easier and cheaper !

Advice: go back to your imaginary world and daydream ... a place where LabRadar and your useless software rule the world of ballistics...leave this stuff to those in the trade. Enough of amateurs trying to pump-up their ego.

 

[TheOfficeT-Rex]

Ah, another thread, another turd argument from authority for the ignore list.

The old lapua data is interesting- if the old standard is 100m measurements that jives with anecdotal “inflated BCs” when truing at range. I find the program gets me close enough to true my software when I don’t have a starting BC. I’d like to do more data gathering with the SD of calculated BCs in the future.

 

[ptosis]

Yeah, sure! have you ever heard of something called COMMON SENSE? I know... may be shocking news to you
[hysterical garbage]

You are arguing with someone imaginary / voices in your head.
SNR = 0, try again.

 

[ptosis]

Ah, another thread, another turd argument from authority for the ignore list.

The old lapua data is interesting- if the old standard is 100m measurements that jives with anecdotal “inflated BCs” when truing at range. I find the program gets me close enough to true my software when I don’t have a starting BC. I’d like to do more data gathering with the SD of calculated BCs in the future.

The question of inflated BCs / significantly higher G7 BCs in the beginning of the trajectory is a tricky one.

While it's certainly true for G1, just by the shape of the reference Cd curve vs. real spitzer boat tail drag profiles, with G7 I would almost expect the opposite (because of higher initial pitch and yaw).

Out of curiosity, I ran G7 BC calculations over the residual velocity data calculated from Lapua Doppler Cd curves -- starting with typical muzzle velocities, for every 100 m. The BC differences over different velocity segments in the supersonic (Mach 1.2+) range are quite insignificant, a fraction of a percent.

For Hornady, on the other hand, for certain bullets (the most striking example is 147 ELDM) the same exercise (based on Hornady's propriteray calculator output) reflects what Hornady publicly announce -- a very high (for the calibre/weight) G7 BC on the first 100 m, drops dramatically (like, 8%) when it gets to 500. The average/optimal BC for the whole supersonic range is, like, 5% less than the most prominent official figure (and perfectly in line with competing products' ballistic performance).

I don't know how to explain it yet. Either the shape of some Hornady projectiles is so particular that it is a much poorer fit for G7 (although spitzer boat tail it is), or some special laws of physics apply to this particular brand, or someone is simply trying to get a competitive edge with "creative" ballistic models. BTW, the BC calculated by Labrabaco in this case is pretty close to the average / optimal BC.

re: SD of calculated BCs -- honestly, I am not very sure it would lead to anything conclusive. My assumption would be that most BC variations in Labrabaco result from the measurement instrument, rather than the measured value (noise due to limited power output, variations in alignment and bore-to-sensor distance, etc.). But that's an interesting question -- would the calculated BC SD be an indicator of the actual ammo quality (that is -- actual BC variation). I will try to dig out datasets for some crappy surplus ammo, and see how it compares to good reloads or Norma/RUAG match.

 

[LastShot300]

You are arguing with someone imaginary / voices in your head.
SNR = 0, try again.

Please not again !

Really? ok...here you go...since you are, at best, simply an ignorant of the topic at hand, just ask Weibel.

Don't take my word for granted...what could I know about this?...after all, my experience is limited to a short 4 years span measuring and processing Mach/Cd data series ...with a Weibel radar...

FFT and SNR...rings a bell? (hint: Doppler radar signal post-processing 101) do yourself a favor and stop posting...or better yet follow the meme!!

 

[ptosis]

Really? ok...here you go...since you are, at best, simply an ignorant of the topic at hand, just ask Weibel.
[mighty frustration and butthurt]

I cannot help but wonder if I am the last person on the Internets who did not tell you yet that you are useless and boring. That would explain your frustration. Why don't you imagine yourself an opponent, and go argue imaginary arguments with voices in your head? -- you seem to be very good at that.

Again: you are wasting my time.

 

[LastShot300]

I cannot help but wonder if I am the last person on the Internets who did not tell you yet that you are useless and boring. That would explain your frustration. Why don't you imagine yourself an opponent, and go argue imaginary arguments with voices in your head? -- you seem to be very good at that.

Again: you are wasting my time.

I may be boring...yes...of exposing your BS time and time again... Your last one on SNR simply proved you are out or arguments and a complete ignorant, just spitting out tons of amateurish hogwash. I have to admit that exposing your rubbish made my day. Next time think twice before posting. It's called USING THE BRAIN...oh no!! my bad!! you can´t find it ...your ego is way bigger !! See you !

 

[ptosis]

Note to self: "Never play chess with pigeons - they knock over the pieces, shit all over the chessboard, and strut around convinced they've won."

 

[category_theory]

Please not again !

Really? ok...here you go...since you are, at best, simply an ignorant of the topic at hand, just ask Weibel.

Out of curiosity are you an engineer? Scientist? Mathematician? Etc.?

 

[LastShot300]

To whom it may concern on using the LabRadar for BC calcs...

"An industry pro that is very familiar with radars (and is a lot smarter than me) told me about some serious limitations of related to using the LabRadar to calculate drag, and I’ll try to summarize what they said: First, he was a big fan of using the LabRadar for what it was designed to do, which is using Doppler to infer an accurate muzzle velocity. BUT, he had a serious issue with people thinking that system could be used for drag calculations. In fact, he thought that “is beyond a crap shoot.” The LabRadar is designed by Infinition, which is the same company that makes the $100,000 models companies like Hornady and Barnes Bullets uses. However, the LabRadar operates at 28 GHz, has a limited amount of power it can push, and has smaller transmitters and receivers – all of which were design choices to constrain costs so they could reach the price point attainable by consumers. It still performs the intended function really well (and is what I personally use ALL THE TIME to measure my muzzle velocity), but using it do to drag calculations is well beyond what it was designed or ever intended to do. The trace file it records has large degrees of uncertainty in it, and while the data is good enough to calculate the muzzle velocity, trying to derive drag from the trace “is more likely to be way off than correct.” Honestly, you need a high degree of certainty in the recorded drag to improve over a BC that was either trued or experimentally measured. Even then, it is a slight improvement … but using a device to calculate the drag that was never intended to do that would likely introduce more error in the firing solution than if you simply used a single-number BC."

Applied Ballistics Mobile Lab – The Future Is Here!

Well, when I started writing that last article on personalized drag models being the final frontier...

precisionrifleblog.com

 

[ptosis]

For the record: I entirely agree with the opinion of Cal from PRB, quoted above, and with the unnamed "industry pro" that he is referring to.

Because of obvious power limits, it is totally illusory to expect Labradar to produce meaningful data for a full bullet-specific Cd/Mach curve, or, as the author specifically defines it further in the text, for "accurate personalized drag model for the full flight of a bullet", which is the subject of the article and of the quoted discussion -- bullet-specific drag models, as a step-up from standard model-based single BCs.

And this is exactly why the ambition of Labrabaco is limited to a single-number BC (imagine big bold red font here).

For the complete picture, the same Cal, in his other PRB article referenced at the link, is referring to the study by Elya Courtney, Collin Morris, and Michael Courtney titled “Accurate Measurements of Free Flight Drag Coefficients with Amateur Doppler Radar” (which, I believe, has already been quoted in this thread), and is saying the following:

All 3 of those researchers seem very accomplished, but for reference Michael Courtney has a PhD in Physics from MIT. In that study, they used a LabRadar, which is a popular consumer-grade Doppler radar that sells for $560, to experimentally determine drag coefficients for fired bullets. The unit takes multiple measurements of a bullet’s speed out to 50-100 yards, depending on the caliber of the bullet, and then it “reverse engineers” the data to determine what the velocity must have been at the muzzle to match the velocities it tracked down range. The researchers basically accessed the raw data the unit records, and did further analysis on it to determine what the drag on the bullet must have been to match how the bullet speed slowed over the first 100 yards. They used that analysis to come up with a BC for a few bullets at a couple different velocities. I spot-checked a couple of the calculated BC’s they published based on the LabRadar data against Bryan Litz’s experimentally measured BC’s in Ballistic Performance of Rifle Bullets – and was shocked to see that they were often within 1% of his measured value or less!

 

[LastShot300]

From the same article already quoted but a few paragraphs later...having the WHOLE picture is the right way to assess things before reaching misleading conclusions.

"Now, that doesn’t mean there isn’t hope! It simply means there are still challenges to overcome. To be clear, I personally don’t believe the current model of the LabRadar is the answer for us recording our own data that could be used to create an accurate personalized drag model for the full flight of a bullet. It is world-class at what it was designed to do: interpolating muzzle velocity from Doppler trace data it collects. I’m a HUGE fan of the LabRadar for that use. However, the internals of the device simply weren’t designed to track bullets over extended distances or to give high degrees of certainty in the drag recorded."

Personalized Drag Models: The Final Frontier in Ballistics?

I am super-excited about this article! I've actually been working on it for a couple of months, and...

precisionrifleblog.com

As I said before, for amateur short-range work, LabRadar may work given its constraints...but for real-world ELR shooting, it is useless.

For a consumer grade unit, ShotMarker works very well. Another option worth a look is the pro grade Oehler System 89, not Doppler-based but still a great choice, nonetheless.

Of the two, I'd go with the first one just because is cheaper and more affordable.