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A couple months ago I purchased a Hornady concentric gauge. I have to say the results for me are as good as it gets. With every answer, comes more questions.

For those of you that use the Sinclair type where the center of the case is the basis for measuring the run out of a bullet. On the Hornady, the basis for measuring is off the back of the case and the point of the bullet, where it not relying on the case body. I question if the readings from the sinclair can be the same as the Hornady. I get shoulder and neck run out, but the bullet is within the .002 I have decided on as a limit.

I will say, the results when shooting my varmint rifles, is that I have been able to do away with fliers, as log as run out is .002 or less. I hope someone has an explanation for the readings with the two types of run out gauges.

Last edited by FredWillis; 04/11/14.
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Stop thinking so much, Fred.


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Can't help it Dave, it is like a disease. Somethings just need an answer.

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One of the factors that has gotten me wondering is the "banana" effect when the case blows out assymetrically in a fat chamber, right above the web. Those cases usually show funny business at the neck thickness, too.
So I don't know which is better, to run on the rim diameter, or around the body above the web, and rest the neck, or spin on the tip. But as you noted, as long as the dial doesn't move much, you are all good.
I have a home-made whatchamacallit that runs off the case base and carries the neck with the bullet. I find TDC with the dial thing running somewhere on the bullet ogive, then poke the bullet in a smooth bullet diameter drilled hole, then yank this way and that. It's a pain, but like you saw, reduces those evil flyers.
I have noticed that banana cases shoot somewhat worse (maybe .3) compared to nice, straight cases. So I have culled some cases simply because they are problem children and will never be straight.


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Dave,thanks for answering. I have been doing considerable thinking about why some use the case body. The first thing that came to mind, was that those who developed these different run out gauges, are generally target shooters. I realize they shoot very high pressures. Since they commonly use high grade brass, measurements of the case body tells a lot. And high pressures will shorten the life of the brass, thus the body measurements.

Measuring on centers like the Hornady, and dealing with less than perfect brass, the run out of the bullet and neck are the most important.

The whole picture is beginning to mature and I think I understand why the two different type gauges both have merit.

Thanks

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Yes, both methods have their pluses. Combined gives you the best total information.
What I really wish for is something where I could spin them, then push a lever and bend stuff straight THE FIRST TIME.

I think you can get away with reading off the case body IF the underlying brass is good -- but that's probably not the situation if the case body blows out sideways on initial fire-form pressure rise.
Anyone is miles ahead if his or her brass is sound to begin with. Brass that was pounded off center in the factory is never going to be match-winning, PD zappin' nirvana.
Another trick is to roll new brass on a level glass or iron surface and see if it stops in the same place three times in a row. Tried that once and yep, the stoppers always formed "off."
Now I check new bags, and if it fails, it becomes SHINY BEAUTIFUL GUN SHOW FACTORY NEW UNFIRED BRASS. No point in wasting components, right?
That said, a tight chamber moderates the blowout problem to a significant extent, the brass simply doesn't get a chance to jump around (and I assume make evil vibrations).


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Dave, thank you for responding. Your insights are valuable to me. I think I am fortunate in three of my rifles have good chambers in them. Two are Bob Green chambered and fitted PacNor barrels and I have little runout problems with the two of them. That of course is shooting fire formed LC cases in the 223 and 20 Tac.

Your idea of rolling on glass or metal to find the cull pieces is a real time saver along with components.

I thank you again for sharing as it is very helpful.


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Come to think of it, you don't really need an absolute level surface...just watch them roll and if they jiggle, they're funny.
Hmmm. Will try just a tiny slope next time and see if that's faster.


Up hills slow,
Down hills fast
Tonnage first and
Safety last.

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