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Bullet spin balancer. Source?

Discussion in 'Ammunition & Reloading' started by Simonpie, Aug 27, 2012.

  1. Simonpie

    Simonpie Portland Active Member

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    Anybody seen one in action? I've heard of them in passing in a couple books, but no serious details or source where to buy. There's a "Jeunke tester", but that is an ultrasonic symmetry analyzer. Not what I'm after. I'm specifically looking at 45-70 heavy bullets, but I'd like to see anything anyone's heard of. I could make my own, but would rather buy.

    Thanks.
     
  2. Mark W.

    Mark W. Silverton, OR Bronze Supporter Bronze Supporter

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    Huh? I been reloading for 40+ years never heard of one. What is it for?
     
  3. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    Are you referring to measuring and adjusting Bullet Run Out? Or a Meplat Uniforming Tool?
     
  4. Simonpie

    Simonpie Portland Active Member

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    This would be used on cast lead bullets for taget or silhouette 200 to 1000 yards. Bullets I've tried run from 450 to 575 grains. Rules require no copper jacket or gas check. Some bullets I cast, some I buy. The goal of spinning would be to identify bullets with voids causing an imblance. I have also seen bullets come out of the mold too hot (soft) and bend on the drop. Measuring runout would identify the bent ones. Weighing might identify voids, but it also might give me a batch that all have similar voids. Just looking for another tool.
     
  5. AMProducts

    AMProducts Maple Valley, WA Jerk, Ammo Manufacturer Silver Supporter

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    So a few years ago I was doing something related, but not really similar, and the idea was to test bullets to their rotational failure point. Which would likely require several hundred thousand RPM. I talked to a friend of mine who designs scientific equipment and has familiarity with some of those cascade centrifuges they use for separating isotopes of uranium. When I gave him the requirements it was kinda like McFly telling the professor the power requirements to make the flux capacitor work.

    So as it turns out, because of the small radius of a bullet, and the insanely high RPM you would need to make these devices just don't exist. Now I did a search for your Jeunke tester and came up with nothing but a bunch of blog posts that make reference to it, and the one useful response I saw was a concentricity gauge that used a feeler indicator that was good to a few tenths (.0001").

    Under the circumstances, I think doing an X-ray or similar radiographic test would actually be superior than a spin balance test. I'm willing to bet if you placed a bullet very accurately within a magnetic field, you could probably determine the particulars of the physical characteristics of the bullet jacket and core density to a greater degree than you could spin balancing a bullet.
     
  6. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    You most be shooting Black Powder Cartridge Rifles matches then!!!

    Okay then, first stop using someone else's bullets! You'll never improve! Us poor boys use certified lead for competition which minimizes variables in the raw materials and then weigh each bullet. Organize your bullets by weight lots and re melt those outside your upper/lower control limits. The key is consistency. Even if all the voids are the same te bullet will be consistent. Get a custom Brooks mold. Buy the best mold, and certified lead you can. Become extremely constant in your casting process and weigh your bullets. Then check for run out and adjust the run out. Consistency is critical not perfection. Shooting technique and having the very best spotter is going to win more matches than anything else. I know from first hand experience.
     
  7. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    If you're buying bullets then remember they're keeping the best ones for themselves! You cannot be a winner with someone else's bullets. Start casting your own and get really good at it!
     
  8. Simonpie

    Simonpie Portland Active Member

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    It looks like that 18" twist at 1200 ft/s gives me 48,000 rpm. I just glanced at my cheapo dremel and it claims 30,000 rpm. This is probably a lie, but it indicates I should be able to buy a motor to get fairly close to the rpm in flight. Of course, just because I can spin it doesn't mean I'll learn anything.
     
  9. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    Let us know how this all works out. What rifle, cartridge, powder combo are you using? What primer, wad, bullet lube?
     
  10. Simonpie

    Simonpie Portland Active Member

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    What are you doing giving me "hard work and careful assembly" when I clearly asked for a gimmicky tool!

    I'm using a Pedersoli rolling block. I've used cases from Starline and Remington and get similar results. 62 grains FFG Kik (I've used Swiss before - similar performance). It really doesn't like more powder. .060 vegetable wad, though it is only slightly better than nothing. I recently tried a bunch of primers. Winchester WLRM and Federal Match are tied for best. It is really sensitive, or there are really bad primers out there. CCI would send them off the paper. Remingtons were decent. I've always lubed with SPG, whether purchased bullets or home cast. I tried over-primer wads. Not bad/not good.
     
  11. OFADAN

    OFADAN Brownsville, OR Well-Known Member

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    Cool. Thx for info. BPCR are my passion! Sorry bout the whole hard work line :). Please resume back to your project.
     
  12. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    You've only gotten part way there when you find a motor that will spin the bullet that fast. How are you going to mount it and keep it centered? The slightest error in this step will result not necessarily in failure of the bullet, but failure of the equipment itself.

    You'll have more luck with just making sure the cast bullets are uniform and without "bubbles" or foreign material entrapped in the lead alloy. Slice a couple of them open and look at them under high magnification. Even a fairly cheap kid's microscope will show whether the alloy was cast uniformly or has voids and crap entrained.
     
    Varmit and (deleted member) like this.
  13. AMProducts

    AMProducts Maple Valley, WA Jerk, Ammo Manufacturer Silver Supporter

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    Depending on how you cut the bullet in half, you can also do a quick "acid wash" with sulfuric acid (battery acid) which will reveal the crystal structure of the material. It's actually quite interesting what happens when you do this. Cast bullets can have huge crystals.
     
  14. Simonpie

    Simonpie Portland Active Member

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  15. elsie

    elsie Way over there on the left Well-Known Member

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    I don't know that anyone actually makes the device you are looking for. The tolerances required to make one that would be effective would put it up there with scientific instrumentation. Basically what you would need is something to hold the bullet almost perfectly centered on or in a shaft based on the external diameter. Then the shaft would spin, but I don't think it would necessarily have to be a high rpm and the heavier the bullet the slower it would need to spin. The shaft would be surrounded by one or more strain gauges that would measure any eccentricity that could be caused by internal voids. The biggest problem is that the slightest variation in the design and construction tolerances would give the same result as an internal void.


    elsie
     
  16. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    And THAT's the problem. I worked 15 years for a company that built balancing equipment. The BIGGEST problem with testing the rotating balance of an object is the precise centering of the object on the test equipment to begin with. It's such a huge problem that even removing the object from the mounting device and remounting it, can yield balance errors that have nothing to do with the actual balance of the object.

    Rotating objects are affected by imbalance more greatly as their diameter increases. Small diameter objects like bullets aren't as problematic as items such as engine flywheels, aircraft propeller's, or turbine blades.

    If the mold was true to begin with then the only variations will be slight bubbles or gaps in the lead. The Mfr will utilize a process to minimize that (such as bottom feed molds) when casting. Swaged bullets which include jacketed bullets rely on the uniformity of the jacket and the quality of the swaging die.

    Rather than approaching accuracy by trying to measure the balance of a bullet, I'd concentrate more on optimizing the stability by matching bullet length and speed to the twist rate of your bore.

    If the need for a bullet balance tester was all that great you'd see them on the market. As it is, they are either almost non-existent, or horrendously expensive "lab toys".

    Of course one could always get an X-Ray system to do their own non-destructive bullet QC. That is if they have a really big check book or a rich wife.:cool: