Checking Runout ?

Discussion in 'Reloading' started by bigrack10, Feb 2, 2009.

  1. bigrack10

    bigrack10 Member

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    Hey guys when checking case or bullet runout, are you suppose to divide the dial reading in half to get the true amount runout?

    Thanks for the help,
    Randy
     
  2. britz

    britz Well-Known Member

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    True runout is how much from the center of axis the case neck wobbles so yes you would devide the total wobble by 2. However, true runout matters only to the one shooting the bullet --> if it works it works.
     

  3. bigrack10

    bigrack10 Member

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    I just bought this gauge and trying to learn how to use it, I wasn't sure how to read it.

    Thanks Britz for the response.
    Randy
     
  4. nheninge

    nheninge Well-Known Member

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    I prefer to sort by total bullet runout. That is the total amount of bullet change where it seats in the cartridge neck. This total runout is the amount of change is ultimately is what will come into contact with the lands of your rifle (hopefully siimulataneously if your bullet has ZERO theoretical runout). Bullets with higher runout at firing have one side of the ogive that contacts the rifling first, thus altering the trajectory of the bullet. I would also bet that bullets with higher runout also have altered vibration cycles (d/t one side of the ogive contacting the rifling first) through the bore. Never heard of anyone testing for this, but it sounds logical.

    If you want accuracy, err on the side of total change. Dividing your runout by 2 might give you a false interpretation that your bullet is twice as good as you think it is. Decide what vital zone you need to hit and build your bullets with whatever it takes to hit that zone within your capabilities. If your long distance range is 200 yards, then the deer/coyote is dead regardless of 1 or 2 or even 4 thousandths runout.

    Use a rifle range and your data to give you your answer.
    TRUST THE SCIENCE!
     
  5. boomtube

    boomtube Well-Known Member

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    There is Total Indicated Runout, what your indicator shows, and run-out, period, which is half the TIR.

    Call it what you want, the handloader's objective is to obtain zero and it matters not how you approach it.
     
  6. bigrack10

    bigrack10 Member

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    Thanks for the response, I will take the indicator reading as what I am looking for.

    Thanks again,
    Randy
     
  7. elmerdeer

    elmerdeer Well-Known Member

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    I thougt total runout was multiply to by 2, so if my guage reads .0015" that means it is really is 003" or is it 00075" need help.
    Thanks
    Elmer
     
  8. nheninge

    nheninge Well-Known Member

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    If your needle moves from 0.087 to 0.091, then the total indicated runout is 0.004 (or 4 thousandths). This is a relative measurement and only indicates change or "out of round" measurements. I don't really understand why you would want to divide/multiply by anything. These devices are typically only accurate to 0.001 regardless.
     
  9. ss7mm

    ss7mm Writers Guild

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    Sometimes, for some, it's easier to visualize if it's in a visual format so.........

    If you had a perfect bullet aligned perfectly in a perfectly aligned case you
    would have something that looks like this. Numbers are for demo only but are actual measured dimensions in the drawings. In this case you can see that there would be "0" runout anywhere you measured either on the case or on the seated bullet.
    [​IMG]


    If you had a perfect bullet poorly aligned in a perfectly aligned case you
    would have something that looks like this. In this case the bullet misalignment pivoted around the base of the bullet. Misalignment would be different depending on what point along the center axis of the bullet the misalignment took place.

    Because the line the measurements are taken from is parallel with the center line of the perfect case/bullet the runout measures the same as if it was taken from the center line. The misalignment is greatly exaggerated to emphasize the misalignment.
    [​IMG]


    You can also see that it makes a difference as to where on the bullet you take your measurements. The TIR will be different for different places. Most people indicate where they take their measurement when stating TIR. I believe you'll find that most people will measure the bullet runout at the juction with the case neck so as to have a consistent place for measuring. Your measurements can be on the bullet or the case but as stated previously, the goal is "0" for all TIR measurements.:)

    If you want to get really carried away you can measure the TIR of a case neck on a loaded round, mark the high point and record it. Then measure the TIR of the bullet, mark the high point and record it. Then what you do with those measurements is up to you but get too carried away and you'll just end up with a headache.:)
     
  10. txlongrange

    txlongrange Well-Known Member

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    Excellent visual post, ss7mm. Pictures are always a plus. :)
     
  11. Derek M.

    Derek M. Well-Known Member

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    I've checked mine 2 ways.

    1) settle the brass only on the 2 cradles and set the gauge on the bullet very close to the end of the case mouth.

    2) settle the head of the case on the rear cradle and the ogive of the bullet right where it exits the case mouth on the fwd cradle and set the guage at the same point. I've even moved the gauge up the ogive just to check for any asymmetries.
     
  12. dmproske

    dmproske Well-Known Member

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    I have a question related to this....

    Depending on what device you use to measure runout, the case body can determine what results you get?

    I use a sinclair runout gauge. The case body rides on roller ball bearings. If there is a high spot or bump on the case body where I am rolling it, it will show on the gauge. I have to really pay attention to make sure I am not getting a false reading.
     
  13. nheninge

    nheninge Well-Known Member

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    Dings just plain suck. I think they are especially evident on the sinclair model with the small bearings (though easier on the fingers). And no matter where you set the blocks, the cases seem to find the dings. Other models just have anodized v blocks that possibly smooth out the small dings, but have their own problems. RCBS casemaster was not sensitive enough for my tastes. I also have wondered if the banana case theory influences case runout. The thin side of the case should stretch and increase runout after multiple firings, especially if only neck sizing. Any input? Never used the Neco gauge. Any experience with this model? Nice pics on the previous post, and thanks for the effort!
     
  14. cabelas90

    cabelas90 Well-Known Member

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    This a great visual aid but its lacking one thing, no criticism intended, but how do you fix runout? :)