FX True Ballistic Chronograph - Testing & Results

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Michael said:
I spoke with Johan about this. It is true that in your scenario much of the results you are seeing are calculated. Here's some more information to help everyone understand this:
  • When setup properly the doppler radar will take hundreds of readings throughout the flight of the projectile (the 1st reading is taken after 10-15 yards).
  • Currently the most accurate readings are at 150y or less.
  • If you notice at the top of the display you see 1/5, 2/5, 3/5. This refers to how well of a reading was taken. 1/5 and 2/5 are really bad and chances are you're getting more calculations than raw data. 3/5 is better, but obviously 4/5 and 5/5 would be best. The raw doppler data can be improved by minimizing interference and properly placing the chronograph in line with the path of the projectile.
  • A new feature is in beta testing that will allow the end user to decipher between the actual doppler data and the calculated data. This will become available as a free firmware download in the near future.
Cheers
-Michael
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Thanks Michael, good data. I've been using mine for quite a while now, and always set it up when I'm shooting bench. I've found a few items from testing.

1. When shooting at "just" 50 yards, the BC will be different than when shooting at 100 yards. It is USUALLY higher when it gets to measure additional data points.
2. I set my distances to 20, 45, 70, and 95 yards. This way at 100 yards, I get the muzzle velocity plus 4 data points. Even when shooting 50 yards, the machine uses 2 data points plus muzzle. If its set like some of the above at 100, 150, 200, and 300, you're not getting the benefit of using multiple data points and only getting muzzle and maybe 100 yards. It's pointless to set it up at farther than 100 yards.
3. MOST of the standard slugs will benefit from using the RA4 profile vice the G1. For boat tails, using the G7 profile will get your most accurate data. Don't let your ego affect your choice, since G1 will give you a higher number!

I appreciate the information of x/5 at the top, I always wondered what that was for...
 
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NAProf said:
Michael,
I believe there needs to be some clarification on how the TB Chronograph takes readings and displays the results. I had a conversation on AGN with one of the developers of the TB App about this very topic. The conversation started because I used the TB when I was shooting some of the AGN 30yd Challenge cards and I had it set up to give speeds at 10, 20, 30 and 40 yds. I shot the target and got velocities at all four ranges - only the pellet stopped at the wood backing of my target at 30 yds. So I figured that the velocities provided were CALCULATE and not MEASURED.

Below is a link to a conversation I had with AGN member "fiske" who stated that he is one of the developers of the software and app for the TB Chrono. He states that because they are sampling at about 1mHz they are doing the DSP in real time and do not store the raw data. So any data that they can output will have significant processing on it (a good thing actually). What I also got from this conversation was that the return signal from the pellet gets worse with range (see the spectrum he provided) and there is definitely a range limit on the radar (appears to be something like 100msec - so at our velocities something like 30-40 yds). So I expect the data it is providing at 100 yds is an extrapolation based on the ballistics calculation. The typical ballistics calculations done on a smart phone are estimates and only deal with drag in terms of known ballistics profiles, not computational fluid dynamics.

What I am trying to say is that while your BC calculation efforts are well intentioned and a good idea, I don't believe you will be able to do what you want with the TB Chrony. I would be happy for fiske or Johann to explain why I am incorrect in my reasoning.

Cheers,
Greg

Whats the actual benefit of the "FX true ballistics chronograph?"

I already have an FX pocket chrono, and a ProChrony. They work fine to tell me my muzzle velocity. The value they provide -> velocity & reg tuning. Power verificaiton for FT and EFT. Benefit of the FX True Ballistics chrony: 1) Provides actual average BC based on my equipment, pellet...
www.airgunnation.com www.airgunnation.com
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After working analysing the data from Doppler muzzle velocity radars for over 20 years, If that is what they are doing, it seems a shocking waste of the radars capabilities. Our experience was that the radar developers are not the best people to analyse the data, that needs to be the ballistic users who know what they are looking for and what the best solution is. The curve fitting for the data is a vital component which can easily give large errors if not done properly. The data does not have to be the exact raw data, the files would be too massive, but it should be available over suitable minute time steps with minimal processing. The true processing can only be done when there is a complete track available, trying to do it in real time will be subject to errors which would be seen when the full track is available.

The radar cannot be used to produce purpose drag laws if that is how they are producing the data, so you are stuck with their choice of reference drag law and their interpretation of how it best fits, or doesn't fit. The Labradar seems to be far superior in its possible uses.
 
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Ballisticboy,
Right on. It’s overkill if I just want a convenient way to get muzzle velocity, but I like my Labradar a lot. At the range, it gives multiple distance velocity readings, which is nice, but most of the work happens later. At home, I transfer the Labradar SD card to my computer and bring up the data spreadsheets for entire shooting sessions. Analyzing the data, I can spot data points that are “bad” and ignore them. It is somewhat laborious, but.using a ballistics app, it’s possible to see which drag model (G1, G7, RA4, SLG0, etc.) best matches the spreadsheet data for a particular projectile and velocity range. With enough data, it’s possible to see subtle trends. After three years of using my Labradar, I wouldn’t settle for any other radar that did not give easy access to all of the raw data.
 
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