Best concentricity gauge?

[asd9055]

So, here is my experience. I have the Sinclair gauge. It was suggested that I check the "concentricity gauge" with a Machinist Gauge Pin, I purchased one on EBay for $10, .9 x 3" approx. Try and buy one the size of your favorite round, you only need this tool once. If fact, you can use mine.

Why, an F class shooter I follow, whom purchases top of the line equipment found his to be "off" by .002 - .003".

He found this with a Machinists Gauge Pin. I checked mine at it was without error. I could not see the needle move and barely "vibrate?". So good gauge then.

So let's go deeper down this rabbit hole. (Every "perfectly" is another 'drink more or less of the Alice's potion for bigger or smaller' and yes, you will find holes in my logic, that's ok)
- if your dies are perfectly concentric, check
- if your brass has perfect neck wall thickness, check
- you resize, somehow spring back is perfectly consistent, check
- bullet (which also is perfectly concentric) is seated by a perfectly concentric seating stem held perfectly by perfectly concentric threads.

So all this was done perfectly, yes?

Now chamber the round, aim, pull the trigger, bang the neck expands to seal the chamber and, Dammit!!! The neck releases the bullet with how many thousandths of potential tilt and misalignment to the bore!?!?!

The argument will be, well I minimized any potential run out with all my prior perfectly's.
At the end of the day, you do you, but have fun shooting, enjoy your (our?) journey in this wonderful world of shooting, thanks to all who have helped me either directly or indirectly with your posts/experience and knowledge.

Happy New Year to all, I hope you had a wonderful Holiday Season!

I am trying to understand the physics of "checking" the gauge with a machinist pin. You mean I can move up and down on a perfect circle, becuase
That what it needs to be to be off

 

[TxPhred]

I put the pin in like you would a loaded round and spin. Needle doesn't move? You got a good gauge system. Then you figure out where your TIR is created.
If the needle moves, your gauge is off and your chasing TIR from the gauge and potentially from the reloading processes.

I hope this clarifies my explanation.

 

[cape cove]

I have been using the RCBS unit for several years. I find it work good only I wish it had bearings rather than v-blocks. I believe it would rotate with less effort. JMO

 

[338 dude]

Mikecr what is TIR?

Total indicated run out

 

[asd9055]

I put the pin in like you would a loaded round and spin. Needle doesn't move? You got a good gauge system. Then you figure out where your TIR is created.
If the needle moves, your gauge is off and your chasing TIR from the gauge and potentially from the reloading processes.

I hope this clarifies my explanation.

Thank you. I don't want to sidetrack. I understand the process. What I don't understand, is what would make a gauge move on a perfect circle " an out of tune" gauge

 

[nksmfamjp]

I was told this is the best but I need both of my kidneys.

Accuracy One Concentricity Gauge

The Accuracy One Concentricity Gauge measures the internal and external neck runout of a cartridge case as well as seated bullet runout.

bullettipping.com

I do not own this one. Looking at its design, I believe it could be the best.

Runout is completely misnomer'd as concentricity. They're not the same thing.
We need straight ammo, which always shows low runout.

Can you explain that? I measure runout with my dial indicator attached to my concentricity tool made by 21st Century. The case is aligned by my interpretation of the chamber datum scheme. So, yes, the gage measures radial runout at a point, but my process is telling me cartridge concentricity as I defined it. Is this what you are trying to say or something I'm missing?

Mikecr what is TIR?

Total Indicated Runout??

Waste of time IMO....but if you think it matters it matters.

Don't you see it on the target? Take your most accurate rifle and make 5 rounds with up to 0.020" runout. Shoot those 5 with 5 good ones. "Believe the Target"

Under 0.007" bullet TIR, I cannot see it at 100 yards.

 

[TxPhred]

Thank you. I don't want to sidetrack. I understand the process. What I don't understand, is what would make a gauge move on a perfect circle " an out of tune" gauge

Ah, ok apologies, it will show you if, in the case of the Sinclair model, (wheels or v-blocks in others), the ball bearings run true and the actual whole unit read out is true, dial indicator and all. That an out of round or untrue alignment does not exist.
These gauges are a +\- reading. An over under off of center.

The machinists gauge pins are held to very tight tolerances. Truly cylindrical and concentric for their length.
In short, you are using a known true cylinder to confirm the gauge's readout is true.

I use my concentricity gauge the first time I use a new set of dies. After resizing, I gauge just below the shoulder, at least at two points on the neck then a seated bullet. If I am within .001/.002. I am good.

Please know I am not a BR or F class competitor. So perfect concentricity is not needed in my processes

Please let me know if I explained this well enough and thanks for considering my opinion.

 

[asd9055]

Ah, ok apologies, it will show you if, in the case of the Sinclair model, (wheels or v-blocks in others), the ball bearings run true and the actual whole unit read out is true, dial indicator and all. That an out of round or untrue alignment does not exist.
These gauges are a +\- reading. An over under off of center.

The machinists gauge pins are held to very tight tolerances. Truly cylindrical and concentric for their length.
In short, you are using a known true cylinder to confirm the gauge's readout is true.

I use my concentricity gauge the first time I use a new set of dies. After resizing, I gauge just below the shoulder, at least at two points on the neck then a seated bullet. If I am within .001/.002. I am good.

Please know I am not a BR or F class competitor. So perfect concentricity is not needed in my processes

Please let me know if I explained this well enough and thanks for considering my opinion.

Thank you for taking the time. I'll get a 308 and a 338 to confirm mine. I am not a competitive shooter of any type. My kids got me the Sinclair on Christmas 2021 and only checked my large magnums. The non-gmanums are "chep shot" meat harversting. I even use factory ammo sometimes.

 

[TxPhred]

Thank you for taking the time. I'll get a 308 and a 338 to confirm mine. I am not a competitive shooter of any type. My kids got me the Sinclair on Christmas 2021 and only checked my large magnums. The non-gmanums are "chep shot" meat harversting. I even use factory ammo sometimes.

I've got the gauge pin if you want to use it. Can't think of any other use for it.

 

[Koda_]

How much does runout affect accuracy?

 

[nksmfamjp]

How much does runout affect accuracy?

My greater than 0.015" TIR at bullet tip rounds shot 3 shot groups greater than 1.25" at 100 yards. My rounds under 0.007" shot better than 0.5" 3 SHOT 100 yd groups. The group in the middle was not quite as consistent, but I believe the target.

I fixed the dies. It worked. I ran out of components to move on. Need more shots to be clear.

for show:

 

[Koda_]

I fixed the dies. It worked.

How did you fix your dies?

 

[nksmfamjp]

How did you fix your dies?

I quite using so much lube….and thinner lube. I started using clamp lock rings and not binding them up on the press and dies. I bought a more accurate MEC press.…probably didn't help. I also switched to Forster dies…..I had them. They consistently produced neck runout of 0.0014" or better. The Redding always had one around 0.0024". None of this is terrible, IME. So, with Forster dies, Creedmoor sports lube and better setup, I'm back in business with tips generally under 0.005" TIR.

i'm holding to get rid of the Winchester WSM brass and go to Lapua….I can probably wait 2 more years…..then probably just change it to a 6mm Creed or 6.5x284 or whatever else actually fits.

 

[Mikecr]

TIR is total indicated runout. This is a quality of roundness, and straightness, and eccentricity (it's the sum of everything).
An item is concentric -only from centerline. A limited attribute.

You can perfectly center a banana, but it's not going to chamber well. It's TIR will be very high.
In contrast, a straight object is low in runout, and therefore concentric. This is what we need (straight ammo).
It can be hard to separate the two in your mind.

We don't need straight ammo to center bullet pointing down a bore. That doesn't happen while ammo rests in a chamber bottom.
The bullets are never really pointed centerline of our bores, and it doesn't seem to matter (within reason).
But what we do need is ammo that is straight enough to mitigate chambered pressure points.
It's only when you run out of chambered clearance for your bananas that results take a hit. It's like pressing a thumb against a chamber in the middle of a group. Chances are POI will shift with that.

This is a matter that goes full circle, no matter your plan. Go bigger chamber clearances, sizing goes up, TIR goes up, but you have more clearance for it. Go tight chamber, sizing goes down, TIR goes down, and this is good because you don't have a lot of clearance for that.
Shoot brass from a sloppy chamber in a tight chamber, it shoots like crap.. Don't do that.
Otherwise, your ammo has to be pretty crooked(relative to clearances) to affect results.

For measurement it's better to consider a v-block setup as a runout gauge. It shows everything.
Our ammo is not straight enough for clearances until measured as such on a v-block.
The neck-benders, which are merchandised as straighteners, do not actually show ammo as straight.
If that seems weird, then check your loaded ammo with a roll down a mirror to see what I'm saying.