Concentricity

Discussion in 'Reloading' started by WV Sendero, Feb 10, 2011.

  1. WV Sendero

    WV Sendero Well-Known Member

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    I just got my Hornady Concentricity gauge set-up and measured the bullet runout on my current load I am working up for my Sendero 7mm. All 25 loads were within .0025, most were .002 or less. Is this an acceptable range?
     
  2. Kevin Rohrer

    Kevin Rohrer Well-Known Member

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    Yes. The rule of thumb is that if it is =<.003, it is fine.

    I use one and my average appears to be around .0015 on the ten presses I measured it with.
     

  3. WV Sendero

    WV Sendero Well-Known Member

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    I saw on here that some people measure the case necks rather than the ogives so I re-measured the cartridges on the necks and the run-out was significantly greater than was measured on the ogives (some were out .007" on necks but none were more than .0025" on ogive). As I did this I adjusted the run-out on the necks to be .0025" or better and when I re-checked the ogives again the run-out was .001" or less on all 25 rounds. So my question is, is it ok to adjust run-out on the necks?
     
  4. Airgunner7

    Airgunner7 Well-Known Member

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    I have one too and it is handy for bending them back but, it will not correct the neck from being off center. I use roller type device to measure the necks. Rolling them on glass is a fast way to check em.:)
     
  5. Mikecr

    Mikecr Well-Known Member

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    You're in position to verify what I've said here all along -that concentricity gages(Hornady, H&H) mask runout. The reason your deviation seems to go up back on the necks is that the indicator is further from the pinned bullet nose. Further back on the body you would see even more, and further toward the bullet tip would show even less -on any ammo -with that gage.
    If you measured that same ammo on a Sinclair roller/v-block type gage, you'd find that your runout is actually greater than you think.
     
  6. Trickymissfit

    Trickymissfit Well-Known Member

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    just fine
    gary
     
  7. frequent misser

    frequent misser Well-Known Member

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    That is a good point. I have both the sinclair and the hornady. Loaded rounds that measure .005-6 on the sinclair show up as .002-3 on the hornady. I loaded some rounds for my 308 the other night and was adjusting my fl sizer. After I loaded some up I checked the runout on both and those were my findings. I need to play with my sizing die some more. I did have the runout down to .002 on the sinclair and I trust those numbers.
     
  8. Mikecr

    Mikecr Well-Known Member

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    Yeah, your ammo is straight when it measures so on this Sinclair(or effective similar):
    SINCLAIR INTERNATIONAL : Sinclair Concentricity Gage -

    They marchandise it as a concentricity gage. Sounds sexier I guess..
    But it doesn't measure concentricity, or eccentricity.
    It's a runout indicator.
     
  9. nheninge

    nheninge Well-Known Member

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    people sure love to see those low numbers. if the machine design masks the run out then the low number doesn't mean anything. it just gives people what they want to see . +1 mike. it also depends on where you take your measurements. run out is always greater further down the bullet.
     
  10. BigJakeJ1s

    BigJakeJ1s Well-Known Member

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    Depends on where the cartridge is supported when you are making the measurement. Some gauges support near the head and near the tip of the bullet. In that case, measuring near the middle between them will give you the largest reading for a given amount of "crookedness". If the cartridge is supported at both ends of the body (below the shoulder) then, yes, further out on the bullet gives larger readings. Beware of trying to compare measurements from two people with different setups.

    Andy
     
  11. Mikecr

    Mikecr Well-Known Member

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    This is true of actual 'concentricity' gages. But you might notice that they typically indicate nearest support of the bullet tip, which provides only a portion of 'crookedness'..
     
  12. Airgunner7

    Airgunner7 Well-Known Member

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    I fell for it too, the hornady gage is cool but not all that practical.

    Buy the Sinclar or make your own with some bb's or V holders.

    Better yet, you have half of what you need on the Hornady already, just add some v holders to it and reverse the concave head holder to the flat side for your end stop......I have a new mission

    Scope rings almost worklightbulb....I'll find something laying around here to mount to it.
     
  13. WV Sendero

    WV Sendero Well-Known Member

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    So is the Hornady even worth having or did I completely waste my money? And is it really a good idea to use it to "straighten" cartridges. It seems like when correcting the run-out with that thing you may cause more distortion in areas you aren't measuring and make your load worse even though the gauge says otherwise. Any thoughts?
     
  14. nheninge

    nheninge Well-Known Member

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    waste of money IMHO. Build them right from the start.