Bullet RUN OUT

L

louisf

Guest
Just a simple question. When I use my sinclair concentricity gauge and the dial indicator reads a total of lets say .004 runout. Is it .004 runout or .002 runout. Half of the total from center?
 
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To the best of my knowledge when you hear the term "runout" it really means "total indicated runout" which is the gauge reading. As you point out that is twice the actual runout from centre but it is still a valid comparison one round to the next so it means as much as halving the number and stating the "real" runout, it just sounds worse !
 
Tir

Actually, TIR means "Total indicator reading". It is stated as such to avoid confusion, such as whether or not the stated value may have been calculated from the actual indicator reading.

The seated bullet almost certainly wobbles, instead of rotating on an axis that is parallel to the axis of the case. Because it wobbles, the TIR will be different over the length of the bullet.

I'd measure (if I were going to bother) as close as possible to where the bullet engages the lands, and leave the indicator arrangement alone while working with a particular chamber (reamer). The actual reading (TIR) will be twice the distance the measured spot on the bullet is out of position.

-Dave-:)
 
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Sure Dave but just because that is the term that you were taught doesn't mean that the other meanings are not equally relevant. I was told a different version by a chap that was taught a different way to you.

I just used that reference bacause it handily had three meanings there. Do a simple google search of "total indicated runout" and you will find screeds of references just the same as if you googled your "correct" version.

Not that it matters ........................
 
It may be a mistake, but when I speak of runout, on a case neck or loaded round measured on the bullet, I mean the total swing of the needle during a 360 degree rotation of a case or loaded round on its longitudinal axis. What makes these numbers hard to compare (from shooter to shooter) is that there is no standard distance from the end of the case neck that indicators are placed to contact the bullet. Generally, the farther forom the end of the neck (on a given round) the bigger the number.
 
Guys,

I don't see it as making a simple thing complicated, it is simply being accurate with the terminology used.

I don't know what you guys understand TIR to mean but at least we have confirmed it relates to the Total Runout that the Indicator will Read !! :)

Bryce
 
If a tree falls in the forest - -

or if a bullet goes down a 22" barrel that is sort of swaging it as it goes along, does one have to be all that concerned about a little runout?
 
adamsgt said:
Where do you position the tip of the indicator to measure the runout?
Click to expand...


I always put the dial probe as far out on the bullet as I can, where any existing runout would give its worse readings. This way when I get a minimal reading on a cartridge.....I know I have one very concentric round.

No sophisticated analogies or definitions to answer your question......just what works for me :D
 
Pete,
It depends on what you mean by a little. Short answer, yes if it is over .002 on the bullet...longer answer, if your loaded round neck clearance is close, and your seating depth is near jam, closing the bolt will actually straighten, to under that limit. Check it out.
 
Hi guys,

..from the pictures I have seen of concentricity gauges, all of them portray the stylus just ahead of the bullet/neck junction.May I surmise this is the incorrect way to check the runout as compared to being farther out toward the tip?
 
Sorta where I was coming from I guess

Boyd Allen said:
Pete,
It depends on what you mean by a little. Short answer, yes if it is over .002 on the bullet...longer answer, if your loaded round neck clearance is close, and your seating depth is near jam, closing the bolt will actually straighten, to under that limit. Check it out.
Click to expand...

I think this may be one of those activities akin to weighing brass and bullets.
 
Two Different Ways

The little Bruno Checker-straightner that is becoming pretty popular simulates placing the loaded round between centers, and indication where the runout should be, where the bullet is inserted into the neck. The design allows for a rather convienient way to straighten the loaded round if needed.
Other fixtures support the case, allowing the bullet to hang out, with the indicator on the bullet tip.
In my opinion, either method will tell you what you need to know, whether the rounds are straight or not. What neither will tell you is where the runout eminates from.
We assume it is at the neck bullet junction. But, if you have ever chucked up a die that has been hardenned, you will find that they are usually not completely round. It is not uncommon to get .0005+ out of roundness after a die is hardened. The cases take this same shape.
If you are turning the case on the "v" block, or points, and it is out of round, then this will show up in the runnout as well. Not much different than rolling something that is not round on a steady rest in a lathe.
All of this probably goes under the heading of being a "non-issue". If your dies are making rounds that are within .001 to .002, by what ever method used, I doubt you will ever see any consequenses on the target.........jackie
 
There are differences in available concentricity guages.
I personally feel that Sinclair's indicates most accurately.

Typical 'between center' systems quite conveniently produce lower TIR readings, followed with assurance as 'better'.
But these are measuring a jump rope's arc nearest it's origin instead of the apex(center peak).

With a cartridge on a V-block or body bearings, the arc is forced out to where we indicate(the bullet), producing far higher numbers. Less is hidden with this.
 
This is all interesting and understandable. Somewhat confussing to the those that
only use them on weekends. First let me add something, I fireform cases
out the back door of my shop, often in winter when there is lots of snow on the ground. I had a favorite pile that I was concentrating on. New cases often lack the total support of the seater and generally don't have low
concentricity readings. When the snow melted in the spring, I was really
surprised to find bullets lying in the grass in perfect shape, complete with
lands marks. Certainly not on all, but some under close scrutiny would show
lands marks, full length that began on the ogive closer to the point than on
the other side. I had heard this before but had never seen it myself.
All a product of runout in the loaded round.
Indicator readings can vary widely depending on how the round is
supported. I have my preferences and I use indicators all day every day.
what you are looking for is the lowest number you can get, no matter
what you want to call it.
 
Some years ago

I was on the sight-in range at the Whittington center and got into a conversation with Skip Otto about using the NECO gauge to measure runout and he showed me how he set up his gauge with two Gem indicators, one on the case and one on the bullet. :cool: Bought another indicator but never got around to setting it up as Skip did. Think I'll have a go at it now. :D
 
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