kiwikid
Well-Known Member
adamjp this is one of the few drawbacks of the LabRadar. Once you start a new series it won't let you go back to the last series and add extra shots.
Calculating BC with LabRadar. It works!
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kiwikid
Well-Known Member
It is possible to go back and look at the previous series but adding extra shots is not possible. Yes it is very frustrating.
RockyMtnMT
Official LRH Sponsor
How far down range are you guys getting vel readings? I have not taken the time since the initial setup to mess with this but have only been able to get a second reading at 25y. I had set the points out to the longest range that it offered. Is there a trick to get readings farther down range?
My settings are 15-30-45-60-75 because I'll normally get readings to 75yds with 284 and larger caliber bullets. I think I was getting to 100yds with 338s. I've learned the unit will stop recording about 5yds past your furthest setting. So mine stops at ~80yds.
The one setting that could affect this is a power setting, if I remember correctly? I've always left it set on the high power setting, but my memory thinks this is related to higher laser powering.
Other than that, I can't think of anything else to be done other than good alignment with your bullet path.
Maybe someone else will pipe up with something more...
oh, and this... When shooting muzzle-braked rifles, do shield the LR from the concussion sideways blast. That could mess anything up, I'd guess. I drove a steel fence post in the ground and using multiple screws, screwed a scrap piece 1"x12" x 24" pine/fir to it to block side-ported muzzle blast/concussion. I kept adding screws until it stayed put. This is left in place where I shoot prone 95% of the time. There are other ways to position the muzzle, or to block muzzle brake blast. LR offers a few suggestions in their literature or on their website.
The one setting that could affect this is a power setting, if I remember correctly? I've always left it set on the high power setting, but my memory thinks this is related to higher laser powering.
Other than that, I can't think of anything else to be done other than good alignment with your bullet path.
Maybe someone else will pipe up with something more...
oh, and this... When shooting muzzle-braked rifles, do shield the LR from the concussion sideways blast. That could mess anything up, I'd guess. I drove a steel fence post in the ground and using multiple screws, screwed a scrap piece 1"x12" x 24" pine/fir to it to block side-ported muzzle blast/concussion. I kept adding screws until it stayed put. This is left in place where I shoot prone 95% of the time. There are other ways to position the muzzle, or to block muzzle brake blast. LR offers a few suggestions in their literature or on their website.
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kiwikid
Well-Known Member
Steve, mine is set up to read 10, 20, 30, 40 & 50m mainly because I have been using it with 22 & 25 cal bullets. As long as I have aligned it correctly I will get readings off of 22 cal bullets to 50m. Initially I struggled with alignment so I cut a piece of brass tube and super glued it into the alignment groove and use it like an aperture sight. Once I did this the readings at the longer distances became a lot more consistent.
Kiwikid.
Kiwikid.
DocUSMCRetired
Well-Known Member
You have to back out, and create a new string.
... digging out this old thread, to add to the original topic.
I am now developing a fully automated Web-based tool (free and open source) to do precisely that: calculate BCs from Labradar tracks.
The calculator uses the G7 model to match the recorded velocities (there's an actual ballistic engine behind), and takes into account the signal-to-noise values provided in the raw track files, to assign more or less weight to more or less trustworthy measurements.
At the prototype stage, results are very encouraging, but -- as drastic anti-COVID-19 measures here in Switzerland kicked in a month ago -- the shooting season ended rather earlier than expected. I do not have enough data to validate the approach or estimate the precision of the tool.
If you have Labradar records of your bullet tracks (the TRK folder on the SD card, "Shot XXXX Track.csv" files), recorded in known atmosphere, I would very much appreciate if you could share them.
In return,
If all goes well, I will make available a calculator producing a BC value from Labradar track files, for all to use under a free and open source license. (If all does not go well, I will produce some text describing the error sources and limitations of the approach, so that others don't waste time where I would have already wasted.)
What is needed:
1. Atmosphere: pressure, temperature and (if available) humidity. This is absolutely paramount, without proper atmo data, the rest of it is useless. An indication of the method used to measure atmo (e.g. "Kestrel 4500") would be very helpful to estimate error margins.
2. The bullet used. Preferable Lapua or Hornady, as they run their products through Doppler radar testing and provide an excellent reference (I believe Barnes and Berger do so too), but any other manufacturer with well-established verified BCs should be good too.
3. The actual track data, a ZIP archive of the whole "TRK" folder (or the whole Series folder) – at least 10 shots of the same bullet recorded in the same atmosphere. The speeds do not have to be consistent or uniform, e.g. loads testing/development data is just fine, as long as projectile and atmosphere are the same.
4. If known, the rifling twist (according to a paper published by Hornady, a rifling twist, which is very different from what is considered "average" for the calibre/speed, could explain a BC deviation of up to 2%).
5. The model of your Labradar: (a) full juice US/CA/AU or (b) castrated EU.
You can send it all by PM here on the forum (it should be possible to attach a file to a message)
or by e-mail to "guns [at] <my user name> [dot] ch"
or simply post here as attachment
Early access to the prototype will be provided to contributors.
Of course, feel free to ask any questions.
Thanks and cheers,
p.
I am now developing a fully automated Web-based tool (free and open source) to do precisely that: calculate BCs from Labradar tracks.
The calculator uses the G7 model to match the recorded velocities (there's an actual ballistic engine behind), and takes into account the signal-to-noise values provided in the raw track files, to assign more or less weight to more or less trustworthy measurements.
At the prototype stage, results are very encouraging, but -- as drastic anti-COVID-19 measures here in Switzerland kicked in a month ago -- the shooting season ended rather earlier than expected. I do not have enough data to validate the approach or estimate the precision of the tool.
If you have Labradar records of your bullet tracks (the TRK folder on the SD card, "Shot XXXX Track.csv" files), recorded in known atmosphere, I would very much appreciate if you could share them.
In return,
If all goes well, I will make available a calculator producing a BC value from Labradar track files, for all to use under a free and open source license. (If all does not go well, I will produce some text describing the error sources and limitations of the approach, so that others don't waste time where I would have already wasted.)
What is needed:
1. Atmosphere: pressure, temperature and (if available) humidity. This is absolutely paramount, without proper atmo data, the rest of it is useless. An indication of the method used to measure atmo (e.g. "Kestrel 4500") would be very helpful to estimate error margins.
2. The bullet used. Preferable Lapua or Hornady, as they run their products through Doppler radar testing and provide an excellent reference (I believe Barnes and Berger do so too), but any other manufacturer with well-established verified BCs should be good too.
3. The actual track data, a ZIP archive of the whole "TRK" folder (or the whole Series folder) – at least 10 shots of the same bullet recorded in the same atmosphere. The speeds do not have to be consistent or uniform, e.g. loads testing/development data is just fine, as long as projectile and atmosphere are the same.
4. If known, the rifling twist (according to a paper published by Hornady, a rifling twist, which is very different from what is considered "average" for the calibre/speed, could explain a BC deviation of up to 2%).
5. The model of your Labradar: (a) full juice US/CA/AU or (b) castrated EU.
You can send it all by PM here on the forum (it should be possible to attach a file to a message)
or by e-mail to "guns [at] <my user name> [dot] ch"
or simply post here as attachment
Early access to the prototype will be provided to contributors.
Of course, feel free to ask any questions.
Thanks and cheers,
p.
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Howland
Well-Known Member
This is a very timely post. Tomorrow is range day. There will be a Labradar.
cohunt
Well-Known Member
I'm following, I'd like to calc bc's for my altitude to see how different they ate from advertised by data...I have a weather meter i can use-- my issue is I work so much I have little time to shoot and record data
Awesome! Thank you!
The more (shots, calibres, rifles) -- the awesomer!
Atmo data is essential. (At the risk of sounding stupid, I implore you to measure station/absolute pressure rather than alt-adjusted "barometric" one. A friend of mine has recently provided a bunch of carefully recorded tracks, with 1011 hPa measured at alt. 800+ m -- all useless.)
cohunt
Well-Known Member
There may be a confusion stemming from Kestrel's "creative" terminology.
There are two types of pressure measures (actual barometers can sometimes show both).
One is the actual pressure measured by the sensor at the location -- usually called "station" or "absolute" pressure -- this is what we need (because this is what defines air density at the shooting spot).
The other is "sea level" pressure. This is a calculated value, basically meaning "what would the pressure have been, if we were at altitude zero / sea level". If you actually are at sea level, station pressure and sea level pressure are the same. If you are at a certain altitude, your effective / station pressure is always lower than at the sea level, but if you know the exact altitude, you can calculate the "would be sea level" figure.
This second "sea level" pressure value is used in meteorology to compare measures of air pressure in different regions / altitudes. It is, however, totally useless for shooting. Bullets only "care" about what's happening at the shooting location.
The problem with Kestrel "creative" terminology is that they are using the term "barometric" (measured with a barometer) to designate the sea level calculated values (and not what is actually measured by the sensors).
The pressure figure that you have posted in the picture, if I correctly read the over-the-pond units, corresponds to station/absolute pressure in Colorado Springs.
(Sorry if all this stuff sounded obvious to you.)
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