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Author Topic: Barrel mounted, electromagnetic chronograph  (Read 17729 times)

Online Steve Blair

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Barrel mounted, electromagnetic chronograph
« Reply #15 on: 10:53 AM, 04/06/12 »
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  • Magnetic fields are a problem in that regard. Field strength diminishes as approximately the square of the distance. So, as you double the distance from 1" to 2", the field strength is 25% of that at 1". In order to provide the field density needed for detection, power requirements increase.

    Light, in contrast, can travel across the universe without energy decrease although it does disperse and exhibit decreased photonic density.

    The easy answer is that light is much more forgiving in this regard than magnetic fields. That does not say that extending the field and detection is not possible. There are well known means of shaping magnetic fields to extend their reach.
    Sleepygator


    Offline walker2713

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    Barrel mounted, electromagnetic chronograph
    « Reply #16 on: 05:42 PM, 04/10/12 »
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  • Well, I promised a report, and this is it. I went to the range this morning with my CED2, and my new Magnetospeed "barrel mounted" chronograph. Here's a photo of my set up...you can see I'm shooting with both chronographs....shooting through the CED2, and the display for each is on the right of the bench. The rifle is a Savage F Class in 6BR, 107gr SMKs, Lapua brass, BR4 primers and H4895 powder.



    I fired 6 strings of 5 rounds each, with charges ranging from 27.5 to 28.5. This is my first work with H4895 for the 6BR.

    Velocity: the average of the Magnetospeed was consitently above the CED2: avg. +.018%. The average ES for the Magnetospeed was 27, and 21 for the CED2. The SD was 7.27 for the CED2 and 10.5 for the barrel mounted chrono.

    Accuracy: shooting at 200 yards, the groups ranged in size from .780 to 1.71, but some of the credit/blame for that should go to your humble reporter. :-[ The bayo mount was very stable on the barrel, and required no adjustment once it was set up.

    I've got the Excel spreadsheets for the two chronos reports, and will email them to anyone who PMs or emails me at gtw217@gmail.com.

    Overall I was pleased with the unit, but think I'll be doing more "side by side" tests in the future. For whatever reason, I have more confidence in the skyscreen unit....but of course for all I know the bayo mounted unit may be more accurate, or the "real" velocity may be somewhere in between.

    Any comments and questions are welcome.

    George

    PEACE: Through Superior Firepower

    Online Steve Blair

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    Barrel mounted, electromagnetic chronograph
    « Reply #17 on: 06:38 PM, 04/10/12 »
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  • George,

    Thanks for the report. H4895 is my favorite powder in 6BR. I'm sure you will find a good load with it. I would expect to correct ~5-6 fps for bullets of that class from 10' instrumental velocity to muzzle velocity, so that may explain the difference. The SD difference is somewhat puzzling. As you said, more side by side is needed.

    Re the H4895: You might try incrementing up a little bit, my loads that gave best results are a little more than yours. If you have them, also try CCI 450 and Wolf/Tula KVB-5.56M primers. Both produce low velocity variation.

    Another experiment to try is shooting the same "known good" load with and without the Magnetospeed mounted and see if accuracy, POI, etc. are affected.
    Sleepygator


    Offline memilanuk

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    Barrel mounted, electromagnetic chronograph
    « Reply #18 on: 08:06 PM, 04/10/12 »
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  • My plan is to try it "as is" and then perhaps adapt it to a small camera tripod, so that the "bayonet" sits just beneath and forward of the muzzle, as it is set up to do.


    If you look here at their setup for shooting with a pressure/test barrell... I'm sure an enterprising individual could make one that works from a given bench rest setup...

    http://www.magnetospeed.com/pages/custom

    I'm *very* interested in the unit personally... between the PITA of setting up a regular tripod mounted chrono -  waiting for the line to go cold, setting it up, aligning it, hoping and praying that either the natural light or the IR screens will decide to cooperate this particular day (and hopefully for the whole string), hoping that the wind doesn't come up and start playing havoc with the tripod and screens (such fun when the whole thing blows over mid string)... not to mention having to play 20-flippin-questions with all the lookee-loos. 

    Something I can strap on the end of the barrel, get my chrono numbers and go home.  Heck yeah I'm interested!

    Offline Nomad47

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    Barrel mounted, electromagnetic chronograph
    « Reply #19 on: 09:16 PM, 04/10/12 »
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  • George, what is the diameter of the barrel at the attachment point? 
    Bill, Retired, AZ/OH
    When guns are outlawed, only outlaws will have guns.
    "No free man shall be debarred the use of arms" - Thomas Jefferson

    Offline walker2713

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    Barrel mounted, electromagnetic chronograph
    « Reply #20 on: 10:14 PM, 04/10/12 »
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  • 1" on the 6br, and I also used it on a Cooper model 21 in 17 Fireball, which was .80...

    PEACE: Through Superior Firepower


    Offline TheSnake

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    Barrel mounted, electromagnetic chronograph
    « Reply #21 on: 12:35 AM, 04/11/12 »
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  • So I take it that this thing is made of some sort of plastic. Looking at the high speed still shots on the web site, you can see the hot gasses and probably flames hitting the read sensor and base. I wonder how many shots it will take before this thing starts to get damaged from the heat?

    George, do you see any signs of this happening on yours?

    I'm not a hunter, I'm a wild game population control specialist.
    Robert Black

    Offline amlevin

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    Barrel mounted, electromagnetic chronograph
    « Reply #22 on: 09:36 AM, 04/11/12 »
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  • So I take it that this thing is made of some sort of plastic. Looking at the high speed still shots on the web site, you can see the hot gasses and probably flames hitting the read sensor and base. I wonder how many shots it will take before this thing starts to get damaged from the heat?

    George, do you see any signs of this happening on yours?

    "Plastic" isn't like it used to be.  Far more heat and impact resistant than that of the past.

    The preferred term today, especially in the gun world is "Polymer".  They even make firearms out of it 8).

    Offline jlow

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    Barrel mounted, electromagnetic chronograph
    « Reply #23 on: 12:18 PM, 04/11/12 »
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  • Thanks for the test and report – much appreciated. 

    I guess one objection I have seen to the barrel mounting system is that it touches the barrel and as a result potentially may have effects on the POI and accuracy of the gun.  Realize that you are only doing load development at this point but a comparison between groups with and without the system mounted might be useful down the road when more finalized loads are available?

    Offline walker2713

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    Barrel mounted, electromagnetic chronograph
    « Reply #24 on: 12:25 PM, 04/11/12 »
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  • jlow: good point.....and I'm planning on doing that test on my next trip to the range....probably tomorrow. 

    I'm going to load 30 rounds with 30.6gr of CFE223, and shoot three five shot strings with the bayo attached, and the same without.....we'll see.

    TheSnake: it still looks new...no apparent wear or damage, though of course it's only had 60 rounds fired over it....

    George
    « Last Edit: 12:33 PM, 04/11/12 by walker2713 »
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    Offline jlow

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    Barrel mounted, electromagnetic chronograph
    « Reply #25 on: 05:44 PM, 04/11/12 »
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  • Thanks walker2713!  Looking forward to you test results!

    Offline walker2713

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    Barrel mounted, electromagnetic chronograph
    « Reply #26 on: 04:58 PM, 04/12/12 »
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  • Here's my follow up report on accuracy with the Magnetospeed chronograph:

    i loaded 30 6BR rounds with 30.6gr of CFE223, and fired 15 rds with the Magnetospeed bayo device on the barrel, and 15 rds without it. In between, I cleaned the barrel and allowed it to cool off, and then fired a fouler. These rounds were fired at 100 yards.

    Here are photos of the targets, and most of the information is self explanatory. I have no (good, i.e. exculpatory :-[) explanation for group #2 on the first target....wish I did.

    You will all draw your own conclusions based on what you see, but I don't see any evidence that having the chrono gizmo hanging on the end of the barrel made any difference in the accuracy.

    (In responding to a question on the Saubier forum, the small caliber folks, the question was raised about whether it would "see" .17 caliber bullets, since some folks had trouble with their skyscreen chonographs with them, especially if lighting was not the best.  I fired 10 rounds of .17 Fireball 25gr Vmaxs with the Magnetospeed, and they all registered normally.)

    Comments and questions are welcome. George



    « Last Edit: 05:48 PM, 04/12/12 by walker2713 »
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    Offline jlow

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    Barrel mounted, electromagnetic chronograph
    « Reply #27 on: 06:17 PM, 04/12/12 »
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  • Thanks for the test and results – looks good to me! 

    A bad group happens, but I too don’t see any evidence of an effect of hanging the electromagnetic chrono off the barrel on accuracy.

    Offline Scotsman1

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    Barrel mounted, electromagnetic chronograph
    « Reply #28 on: 06:36 PM, 04/12/12 »
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  • Thanks for your work between setup and all the posting. Its been really helpful. I know I hate to crony because of all the setup BS we gotta go through.

    Really appreciated.
    BTW, how do you like the new CFE223?  I mean overall... Have ya tried it in anything else other than 6BR and 30?

    Cheers,
    Sean
    Save a seal, club a Liberal!

    Offline Nomad47

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    Barrel mounted, electromagnetic chronograph
    « Reply #29 on: 07:17 PM, 04/12/12 »
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  • George, was there a POI shift or did you make a scope adjustment between the two sets of groups?  Or just change aiming point?
    Bill, Retired, AZ/OH
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    "No free man shall be debarred the use of arms" - Thomas Jefferson


     

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