Concentricity gauges, let's hear it if bench loaders and accuracy guys....

I am not the guy to ask, but this subject has interested me lately. A buddy of mine loaned me a Sinclair.
So, I have been watching YouTube videos and there are several out there that are made by small shops and not the major reloading manufacturers and they look to me like they would be easier to use than this Sinclair.

So, I am basically tagging this thread to hear the answers.
I was actually going to start a thread just like this over the last couple days and never got around to it.

On a related subject, I would be interested in hearing what kind of concentricity other people consider to be adequate and realistic. I am not a formal benchrest shooter. I am a guy shooting "regular" guns who loves accuracy. I don't hunt, or compete; but I shoot probably four days a week at paper and steel and am trying to up my game in the reloading department more so than the gun department. I would also like to hear what you can do to improve concentricity: there are all kinds of videos about the various gauges as well as how they work: but almost nothing about how you can get better concentricity.

I just ordered a 12FV in 308. I also have a Savage in 6.5 Creedmoor.

Ironically, the thing I have been trying all this stuff on is a Ruger American Rifle in .300 AAC Blackout. Why ? Because it didn't shoot very well and I was trying to figure out how to make it shoot well. And I have come leaps and bounds over the last two months of playing around with it. I started weighing my cases, then I just cut to the chase and bought Lapua cases. I am sizing them in an LE Wilson hand die on an arbor press. I have cut my group size more than in half by playing with loading techniques as well as trying all kinds of bullets/powders/primers.......................

The 6.5 Creed shoots pretty damn good as is, not that it couldn't be better. But, just like you, I am going to figure all this stuff out and then apply it to the 6.5 and the .308.

As I've said. . .

I wondered this exact wonder this past year, so I did an experiment!

I built a concentricity gauge and characterized a couple batches of ammo for my R700 SPS Tac (.223 bull barrel), benched and bagged. In a batch of 50 rounds I separated into 3 tranches, A: 0-3, B: 3-10, and C: 10-30; units are 0.01mm of runout, measured at the leading edge of the bullet's major diameter vs the case shoulder and case base.

I found. . . no difference whatsoever in group size! I shot the groups across 3 range trips, A, B, C, B, A then C, B, A, B, C, etc. I was a rigorous as possible within the constraint of 50 rounds (and I design test plans for a living).

I'm certain that concentricity effects accuracy, but I have proven to myself that with my equipment and my average group size of ~1 MOA, it's not measurable. After I've shrunk my groups down to ~0.75, I"ll rerun the experiment and see if I can measure the effect.

If you don't yet have a gauge, save your money and do your own experiment; take a batch of 50 identical rounds and separate them visually by rolling across a flat surface and looking for wobble. Shoot your 10 best and 10 worst, and see if you can measure a difference.

Edit: I also found that, just as Redding will tell you, the vast majority of runout is caused by brass (neck thickness and modulus variation) and the sizing die. The seating die doesn't seem to matter at all. This discovery cost me a $100 Redding seating die; it's wonderfully adjustable, precise, and repeatable, but the ammo it produces is no more concentric than what I make with my roughly-finished Lee seater.

I went through this awhile back and built two different styles.

This is the first one, 4 ball bearings, 3 hunks of aluminum, 1/4" dowel pin, 1/4" stainless rod threaded on one end and two socket head cap screws. It's very versatile as I can measure from .17 hornet to 50 BMG, just the case alone (inside or out) or a completed round. I can also move the front support to different locations so it's easy to go off the neck, shoulder or anyother area on the case.


Shortly after that I added another post that holds a disk of aluminum and used an o-ring for a "tire", makes it easier to use.


Then awhile after that added another accessory that slides over the dowel and extends back to the indicator tip, where the two bearings contact easy other. Allows for a very fast and non destructive way to measure case wall thickness.



Then I built this one that is super easy to use but only works on loaded rounds and not as many as the first one.


Results with ammunition with differing runout have other variables. If the rifle won't shoot well with perfect ammunition, "bad" ammunition doesn't seem to hurt it as much. Also when testing ammunition of differing amounts of run out, it's worth measuring runout, then chamber and remove the round and remeasure.

With more than one combination I tested, runout went away after being chambered. If that is the case in the observation above, it's not that runout doesn't matter, rather it was "fixed" when chambered.

I don't think one "needs" a runout gauge but one can answer questions that are difficult to answer without one.

I also think it's worth measuring runout of a fired case, then one that is sized with the decapping pin/expander removed and then one with the decapper/pin installed. If you can't get good results at this point, they don't tend to get better down the line.

Here's what I observed when I went down this rabbit hole last year (BTW, I'm still down here with the rabbits). TIR noted on 3 each 10 shot groups using 168 Berger VLDs in my FN SPR .308



It's enough of a difference for me to keep measuring and correcting it. I use the Hornady tool to do that



Please, someone show me that this is a waste of time. I'd love to quit doing it as it's a tedious process to measure and correct every round

None if you aren't shooting bench rest matches out of a bench rest rifle. No point to any of that kind of stuff for an entry level hunting rifle like an SPS. Barrels aren't up to bench rest accuracy. Most of those assorted gauges are primarily about separating you from your money.

True. We're not talking about affecting accuracy that would concern someone who's sticking 3 rounds in a paper plate at 50 paces and calling it good

Walkalong said:

But the OP is asking for friendly feedback, not a blanket "your wasting your time" statement.

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Mr. Walkalong is making a valid point, which I second. A runout gauge, when understood and used properly (Another matter) can supply valuable feedback on one's loading equipment and loading techniques. Attached is a photo of a runout measuring instrument made by Ferris Pindell, a master machinist and accuracy expert who, among other accomplishments, was co-creator of the PPC cartridges. Note that the indicator is positioned at the tip pf the bullet.

I have the Sinclair and the Hornady - buying the Hornady second for the ability to correct run out - which I've largely discovered is not much more than marketing. In tests similar to Nature Boy's, I have noted better performance from lower run out, but only if the ammo left the press with low run out, and "correcting" it with the Hornady tool hasn't proven to close that gap for me.

There are FAR more critical contributions you can make to improve your precision than adding a concentricity gauge, however.

i use an rcbs concentricity gauge. i'll take anything less than .003" runout. anything over that i use for things other than small groups. i also turn necks and uniform primer pockets.

i'm an old varmint shooter and have been chasing small groups for 50 years.

luck,

murf

Nature Boy said:

Here's what I observed when I went down this rabbit hole last year (BTW, I'm still down here with the rabbits). TIR noted on 3 each 10 shot groups using 168 Berger VLDs in my FN SPR .308

View attachment 762702

It's enough of a difference for me to keep measuring and correcting it. I use the Hornady tool to do that

View attachment 762703

Please, someone show me that this is a waste of time. I'd love to quit doing it as it's a tedious process to measure and correct every round

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not me!

murf

I think striving for straight ammo can never be bad - just another step in making the best ammo you can (if that is your aim). A modern press and dies, along with good brass and bullets will mostly produce good ammo out of the box. If, however, you want "better" you need to pay attention to the details. Many steps in the case prep procedure are difficult to quantify, primer pocket uniforming, flash hole deburring, etc. etc. but when you have that round in your hand on the 1000yd line, you know if any thing goes wrong, it's not the ammo.

Here's a couple of my homemade concentricity gauges.

Does any of the gauges check to see if the base is square? All of the ones I've seen just ride against a stop. I would think a more accurate setup would hold the cartridge base square. Then you see the whole picture. But if your shooting a gun that has been blueprinted you are square. For the common folks this is where probably the most error is out. If you don't start off square, everything is off.

^ Top shelf craftsmanship on both of those.

Many steps in the case prep procedure are difficult to quantify...

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And that is the reason I made the ones I have. To get real numbers when changing the various numbers vs just thinking something is better.

Once I had a way to measure finished product with precision I had a better understanding of what makes things better or worse.

For example I now know what dies are used makes a larger difference than the type of press I use.

So I can put good dies in a progressive and turn out more precise ammunition than I could with a lesser set of dies in a single stage. The huge gain in production cuts reloading time much more than it took me to build the tools and test things. So for me at least, it was and investment of time I have gained back many times over.

Does any of the gauges check to see if the base is square?

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If the base is not square the case will move back and forth because they are tapered and only contact the rear post at one point. Any back and forth movement on a tapers part will register on the indicator.

The Hornady tool locates off the case rim and bullet tip using a taper on both ends.

Even though I sort of proved to myself that doing this is worth it if your goal is chasing perfection, here's why I think it's a bit of a fools errand.

I'm correcting to achieve a total indicated run out of 0.001 or less. This is a non linear measurement meaning that we're talking 0.0005 per side.

Seriously.

Perhaps one less cup of coffee might make more difference down range.

That said, I'm still doing it.

Nature Boy said:

The Hornady tool locates off the case rim and bullet tip using a taper on both ends.

Even though I sort of proved to myself that doing this is worth it if your goal is chasing perfection, here's why I think it's a bit of a fools errand.

I'm correcting to achieve a total indicated run out of 0.001 or less. This is a non linear measurement meaning that we're talking 0.0005 per side.

Seriously.

Perhaps one less cup of coffee might make more difference down range.

That said, I'm still doing it.

Click to expand...

Personally I never bother to correct them if they're wonky, I mark them and use them for fouling shots etc.. I use the gauge to find out where the error is creeping in and fix that, once everything is set up well then the gauge is rarely needed.

I would be concerned that pushing a crooked round straight would vary the neck tension.