Comparing 3 Chronographs

Discussion in 'Main Message Board' started by AAA, May 29, 2018.

  1. AAA

    AAA Silver $$ Contributor

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    We all have our favorite chronograph. Each gives a number, but how would that number compare to the same round fired with another chronograph. I wanted to know so a friend (Rand Fishleder) and I set up the following test.

    We used 3 instruments and my 6mm BRA F-class rifle with fire formed brass and 200 rounds on the new barrel.

    Oehler 35P
    MagnetoSpeed - V3
    Lab Radar

    5 rounds were fired to make sure all systems were recording and to warm the barrel.

    Then the test was 20 shots fired across all three instruments with 45 seconds between shots.

    The Oehler was set 7.5 yards from the muzzle so 12 fps were added to the recorded value to get back to muzzle velocity.

    Results are attached.

    Judge for yourself, but I was impressed by all.

    Randy Snook

    [​IMG]
     

    Attached Files:

    Last edited by a moderator: May 30, 2018
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  2. Regnar

    Regnar Silver $$ Contributor

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    Just wondering if the addition of 12fps is the correct number. the es and sd numbers are almost identical with the Ohlers avg velocity lower.
     
  3. Esoteric Junkie

    Esoteric Junkie

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    Now take the Oehler and put it on an eight foot bar.
     
  4. ED3

    ED3 Gold $$ Contributor

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    Given the Lab Radar also doesn't read velocities at the muzzle, why modify the Oehler data, and not do something similar with the LabRadar's numbers?
    isn't the LabRadar reading the velocity out around 50'?
    If so the velocities recorded on the MagnetoSpeed and Labradar should be quite different, if you're accurate in assuming 12fps for approximately 1/2 that distance.
    Nonetheless interesting.
     
  5. Texas10

    Texas10 Gold $$ Contributor

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    Very happy to see your numbers support my decision to buy a Magnetospeed, on sale yet. Had read reports comparing it to the Oehler and the numbers I get seem to be supported by my long range shooting results.
    Many thanks for taking the time and effort, not to mention cost of preforming this comparative test. Always good to get actual test results.
     
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  6. Ksracer

    Ksracer

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    It tracks the bullets speed decay from when it first picks it up until it's out of range, and computes a MV from that info.
     
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  7. AAA

    AAA Silver $$ Contributor

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    Using the Berger Ballistics calculator with the 105vld and a Muzzle Velocity of 3000 fps at 10 yards it projected a velocity of 2983 losing 17 fps. With the Oehler 7.5 yards in front of the muzzle adjusted approximately 3/4 of 17 = 12 fps.
     
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  8. AAA

    AAA Silver $$ Contributor

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    We were using the internal trigger on the lab radar. The manual says the Vo indicated is the actual muzzle velocity when using the internal trigger, but not if using the doppler.
    The Oehler adjustment was based on the Berger Ballistics calculator.
     
  9. Forum Boss

    Forum Boss Administrator

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    AAA, do you have any photos of your set-up? I think many readers would be interested.

    FYI, some years back we did a six-chrono comparison. Even built a custom test rail so we could mount them all inline. This was before the days of LabRadar.

    We had: Oehler, Shooting Chrony, Kurzzheit BMC, Caldwell, CED Millenium, and a magnetospeed on the rifle. After two weekends, and scads of data, we really were not able to conclude much -- all the units had a few "drop-outs" or weird values that sort of happened unpredictably. The Kurzzheit and Oehler did seem the most precise. The Magnetospeed was certainly the easiest to set up.

    Never ended up doing a full write-up because the data was so overwhelming, yet really didn't provide meaningful distinctions.
     
  10. Dusty Stevens

    Dusty Stevens COVFEFE Gold $$ Contributor

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    All of mine have been within tolerance so i just use the labradar now
     
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  11. AAA

    AAA Silver $$ Contributor

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    Added a photo to original post

    Boss: Thanks -- I inserted that photo inline as your original attachment was quite large.
     
  12. powderbrake

    powderbrake Gold $$ Contributor

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    AAA did a great job of comparing the 3 chronos. What conclusions can be drawn?

    1) It is a comparison, I have not checked the manufacturer's claims of accuracy, but the 3 chronos are very close to one another. There is no way for us to determine the actual true velocities, but we do not need to do so. Any of the chronos would be more than adequate for an accurate shooter.

    2) The resolution of the units is actually pretty astounding. One foot per second is a resolution of 0.033%

    3) AAA did a great job of reloading a very consistent round. With an extreme spread of 33 out of 3014 for 20 rounds, that is only 1.09% total spread of velocities.

    4) There is a closer velocity match between the Magnetospeed and the Lab Radar, but that does not mean the Oehler is less accurate. There is simply an offset between the Oehler and the other two. This could be due to the greater distance, the location or the internal working of the Oehler.
    I modified the Excel worksheet to show the differences, again they are amazingly small between the M and the LR, and would be similar to the O with an additional 10fps offset.

    5) Believe your chronograph, it is probably the most accurate reloading tool that you own.

    Brian Litz of Applied Ballistics carefully explained the operation, set up, accuracy and comparison of there Chronographs in his books. They are well worth the money, and give great insight into the workings of chronographs.

    Again, AAA did a great job on this comparison, and I ask your forgiveness for modifying your excel sheet.
     

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  13. Bbear

    Bbear Gold $$ Contributor

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    I read somewhere (wish I could find the article) that the Oehler and other 'stand alone' Chronographs have between a 1-3% difference in what the MV is. Looking at the tables, the Oehler is definitely under the 1% range. That's making an assumption that the Magnetospeed and the Labradar are 'more' correct. Still, a great report on what they will all do.
     
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  14. Legionnaire

    Legionnaire Silver $$ Contributor

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    Very interesting; thanks! Looks like a slightly-more-than-12-FPS adjustment to the Oehler might be in order. Nevertheless, very encouraging to see the high degree of consistency.
     
  15. BIG D

    BIG D Gold $$ Contributor

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    AAA you don’t have your blinder on! Therefore I say results are defunct. At least you must have had clean glasses and not a torn retina or something! LOL
    Great test and thanks for sharing. I’ve tested my magnetospeed and Labradar together and results are always within 2-4 FPS of one another
     
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  16. AAA

    AAA Silver $$ Contributor

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    BIG D - the NEXT X blinder was on, visibility was good = Quality results

    [​IMG]
     
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  17. Elwood

    Elwood

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    I have done the same but only for a few shots as I was curious. The Labradar and Magnetospeed were both consistent, the Oehler less so., although I did test the Oehler against the Magnetospeed a year or two ago and the Oehler was consistently 10-15 fps below the Magneto.
     

    Attached Files:

  18. PatMiles

    PatMiles Gold $$ Contributor

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    I did a 4 shot test with my Magnetospeed and another shooters Labradar a couple of days ago. The results were within 4 fps with the LR being optimistic. My curiosity was somewhat satiated.
     
  19. dedeadeye

    dedeadeye Gold $$ Contributor

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    Randy, very nice job. You have answered a number of questions many of us had. Thank you.
    Roger
     
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  20. hoz53

    hoz53 Gold $$ Contributor

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    nice job and thanks for the effort. for me this confirms my labradar is plenty good and i dont need a magnetospeed hanging off my barrel influencing poi.
     
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