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Thread: Bullet weight vs. ROF

  1. #21
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    Vegas SMG's Avatar
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    The single 50 round box of 124 grain NATO I used was supplied by Brother Evil. Thank you sir!

    It was German MEN and is very hot. In fact, I found it too hot to use for anything other than my testing. It *could* damage guns not rated for +P+ and I will not use it with the A bolt where I found the recoil impulse to be much too violent with the bolt smacking hard against the rear of the lower receiver. The possibility of accelerated wear and tear just arenít worth the price of admission for me, As you can see, itís much hotter than the Winchester +P Law Bob referenced, but Iíve also seen it listed as being slower than the specs Iíve posted. All I know is what I felt. Itís hot.

    Caliber: 9mm Luger (9x19mm, Para, Parabellum)
    Bullet Weight: 124 Grain
    Bullet Style: Full Metal Jacket (FMJ)
    Bullet Casing: Brass, Reloadable
    Bullet Primer: Boxer, Non-Corrosive
    Muzzle (Velocity): 1284 fps.
    Muzzle (Energy): 461 ft. lbs.
    Very clean
    New manufacture
    Manufactured in Germany
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    Last edited by Vegas SMG; 07-05-2018 at 07:15 PM.
    Please visit my FB page for the latest CF-W bolt information.
    https://www.facebook.com/VegasSMG/?ref

  2. #22
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    What's missing from this thread is ROF data! Where are the timers? Aren't there any engineers 'round heah? To start with I would choose three variables, two levels: 115gr vs 124gr, two different ammo manufacturers, and two subguns, and run a 2^3 factorial experiment measuring ROF with a pact timer... Then we could begin to talk turkey relative to the OP's question. I know - "OK nuge, knock yourself out!" Heh-heh maybe I will.

  3. #23
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    Quote Originally Posted by nuge View Post
    What's missing from this thread is ROF data! Where are the timers? Aren't there any engineers 'round heah? To start with I would choose three variables, two levels: 115gr vs 124gr, two different ammo manufacturers, and two subguns, and run a 2^3 factorial experiment measuring ROF with a pact timer... Then we could begin to talk turkey relative to the OP's question. I know - "OK nuge, knock yourself out!" Heh-heh maybe I will.
    Well its now the 19th of July and we are still waiting ???????
    WE WON !

  4. #24
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    Quote Originally Posted by anm2_man View Post
    Well its now the 19th of July and we are still waiting ???????
    Who's we??

    Working on it... Ammo manufacturers will be Federal AE & SIG. Subguns will be Uzi & Sterling. Figure of merit = ROF (rounds per minute). I have two timers, but will probably go with just the PACT. All materials are ready. Experiment design is as below...

    Any Predictions?

    Please carry on with the energy, dwell time, pressure, burn rate and charge debate... OP, please pardon my indulgence with your thread. Meanwhile I will post the results whenever I obtain one of those round tuits.

    Last edited by nuge; 08-06-2018 at 10:14 PM. Reason: replacing accid. deleted picture

  5. #25
    Registered User xdamagedx's Avatar
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    Thanks for taking the time to do it!

  6. #26
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    Got 'er done! All completed with some surprising results. 30 strings were tested: 24 for the original experiment and 6 additional tests of Fiocci 158 subsonic, 3 with each subgun. Here are a few pictures and vids of a couple strings. Data will follow...







    https://photos.app.goo.gl/hB8n9CK6eAvGTbwF9

    https://photos.app.goo.gl/SkmSXtpYyGDRh5kA8
    Last edited by nuge; 08-26-2018 at 12:13 AM.

  7. #27
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    Factorial Experiment Explanation

    In case you are not familiar with this experiment design approach I want to explain an important concept about factorial experiments. This may help to understand the data, results and analysis when I post them.

    This experiment is laid out such that all of the main variables can be analyzed independently. In this case they are (A) Bullet Weight; (B) Bullet Manufacturer; and (C) Subgun Type. Not only that, every combination of these 3 factors can be analyzed independently of each other including all of the two-way interactions and even the 3-way interaction.

    These vectors are shown as the plus and minus columns in the picture below for this experiment design. All possible factor interactions have their own column including the one circled on the far right - the 3-way interaction.

    How can all of these factors be independent from one another? It's really math (linear algebra). You math guys may remember that the test for independence (orthogonality) is to take the dot product of any two vectors and it will = 0 if its orthogonal. You can try this with with any two columns in the experiment and the result will be zero.

    Anyway, factorial design is a powerful method of experimentation used in science and manufacturing, and can reveal a whole lot more than the traditional one factor at a time experimentation. This will make more sense when I show the results...


  8. #28
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    Here is the raw data from the experiment. It also includes the sequencing and order of the tests as they were planned and performed. I will follow up with some analysis a little later...


  9. #29
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    Averages and Effect Calculations

    The replicates of the various runs were averaged, than a grand average calculated (1st pic). Then each independent factor gets its own "effects" calculation (2nd pic). These effects will then be sorted and analyzed for significance in the concluding post about this experiment.




  10. #30
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    Results

    The "needle mover" for ROF that significantly dominates this experiment is the three-way interaction between subgun, bullet manufacturer, and bullet weight. If you remember this is the ABC interaction vector that I mentioned in a previous post. Although this is possible and occasionally happens, it is rare to have such a three way interaction as the dominant effect in a factorial experiment.

    But, in fact, it IS the dominant one in this case. And it begs the question: Why does the unique combination of Uzi, SIG Manufacturer, and 124 bullet weight send the RPM skyrocketing + 130 or more RPM to exceed 700 rounds per minute?

    Subgun by itself is the next most significant variable in terms of impact, and is only slightly behind the 3-way interaction in terms of effect on RPM. The large RPM increases were seen only with the Uzi.

    In the "possibly" significant category are two, 2-way interactions: Subgun x Bullet Mfr and Subgun x Bullet Wt. Verification of significance for these two factors will require analysis of variance calculations to confirm.

    Bullet weight and bullet manufacturer by themselves were relatively insignificant in affecting ROF. Tests were added as a reference for Fiocci subsonic 158 gr ammo. These showed no elevation in ROF in either the Uzi or the Sterling. Remarkably, the Uzi and Sterling have a base ROF nearly the same, except for the unique combination mentioned above. And the Sterling ROF seems undisturbed by any changes in bullet manufacturers or weights.

    At this point if I were to try to answer the OP's original question, I would say that Bullet Weight by itself will probably have no significant impact on your RPM. But depending on your gun, and the complex interaction between your gun, ammo, and ammo manufacturer you could be in for an RPM spike.

    Of course all of the normal engineering caveats apply about not extrapolating these results to other guns and ammo not studied here. But I'll bet if you have an Uzi that you can accelerate its ROF by using 124 grain SIG Elite performance ammo.

    Thanks to the OP for this provocative thread. Also thanks to J. Crew (Crew Eng) for support with the field work, pics and vids.

    nuge

    Last edited by nuge; 08-07-2018 at 04:50 PM.

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