Warning: Chronograph issues

fancygunz

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May 6, 2019
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This is just a warning to those who (like me) might put too much faith in their cheap Caldwell Ballistic Precision chronograph. You might say "well obviously it's a cheap POS based on the price" but I have trusted it for many years and it was good enough that I didn't really notice a major issue. Maybe others also have this issue with other chronographs as well, I don't have any experience with anything else.

Basically it detects different velocities based on where in the "detection area" I shoot, based on my point of aim. If I aim at a target which goes through the upper portion of the chronograph, that group will show a pretty good SD/ES. I then shoot the same exact load/rifle combo at a different part of the same target, which might go through the lower portion of the chronograph, and that group will also show similar SD/ES BUT a very different average velocity.

For example:
Group 1 shot at top left of target
2555 ft/s AVG
23 STDEV
51 ES

Group 2 shot at middle of target
2600 ft/s AVG
23 STDEV
56 ES

Group 3 shot at bottom right of target
2502 ft/s AVG
12 STDEV
31 ES

Calculating all groups together as one data set
2552 ft/s AVG
47 STDEV
152 ES

You can see that within each group, the SD/ES is pretty consistent. Taking all velocity values of the 3 groups and doing the math as one set of data makes the load look awful. I can shoot 5, 10, or 20 shots at the same point of impact and get similar average velocities. As soon as I change point of aim (bullet crosses chronograph at a different location) I get a shift in velocity.

Waiting for the Caldwell VelociRadar to be released before I decide whether I want one of those or a Labradar.
 
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Superjet

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Mar 9, 2019
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I have one of these and it was one of the most frustrating things I've ever owned. Random misreads, sensitive to light conditions, etc. The app was very good though. I bought a magnetospeed sporter to use in the mean time until the Velociradar is out, and have been happy with it.
 
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CoryT

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  • Mar 5, 2004
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    All multi sensor chronographs are sensitive to angular error, the shorter the base length the greater the error. For precision, the bullet must pass over the sensors straight and level. The actual height over the sensors is not an issue as long as the sensors can be tripped. Shooting at any angle other than 90 in both L/R and U/D axes has the effect on increasing the sensor separation and showing a lower velocity than actual. This is why a long screen separation is helpful, and the Oehler for example allows screens to be as much as 12 ft apart.
     

    Emmaandhaley

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    Dec 30, 2018
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    Maybe I’m not good at math but to me your numbers do not add up.

    If I take average of the 3 groups you posted I get

    25552
    19
    46

    so this tells me something does not add up.

    I think most of us did at one point have the Caldwell. Some of still do and some of moved up to bigger and better things.
     

    fancygunz

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    May 6, 2019
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    I have one of these and it was one of the most frustrating things I've ever owned. Random misreads, sensitive to light conditions, etc. The app was very good though. I bought a magnetospeed sporter to use in the mean time until the Velociradar is out, and have been happy with it.
    Unfortunately it's hard to attach a magnetospeed to my barrel when it's 100% covered by the handguard.

    I love my LabRadar ... and that's all I'll say about that.

    Optical chronos suck ass. So glad we have the labradar now.
    I might just have to suck it up and get one. I was hoping more info about the Velociradar would be out by now.

    Maybe I’m not good at math but to me your numbers do not add up.

    If I take average of the 3 groups you posted I get

    25552
    19
    46

    so this tells me something does not add up.

    I think most of us did at one point have the Caldwell. Some of still do and some of moved up to bigger and better things.
    That's not how it works, you can't just average my averages. ES is extreme spread, you need the individual velocity measurements to find min and max velocities. Same with SD, you need all the data. You are right about the average velocity though, I had a typo. Meant to type 2552 but wrote 2542.
     

    Dawhit

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    Nov 4, 2019
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    Checked my Caldwell vs Mag V3 one evening. As the light faded, the Caldwell progressively gave slower velocity numbers, while the V-3 numbers stayed consistent. By the time it was gloomy enough that the Caldwell wouldn’t pick up a reading, it was nearly a 100fps slower than the V-3.
     

    smoothy8500

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    Warning: A sample of numbers that shows a high "spread" and SD pretty much means that a bunch of samples are going to appear completely unrelated to race other.

    Yes, optical chronograph are affected by light and angle, but your reloads are not a reliable indicator that it's entirely the chronograph issue.
     

    fancygunz

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    May 6, 2019
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    Warning: A sample of numbers that shows a high "spread" and SD pretty much means that a bunch of samples are going to appear completely unrelated to race other.

    Yes, optical chronograph are affected by light and angle, but your reloads are not a reliable indicator that it's entirely the chronograph issue.
    These are factory Federal Gold Match 185gr Berger Juggernauts.
     

    smoothy8500

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    Oct 10, 2012
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    Yes, FGMM can have wide ES/SD and your findings could still be within the range of possible velocities. It's possibly the chronograph, but it could be the ammunition.