Concentricity Gage Advice

[brando]

Does anyone use a concentricity gage in their match load development? I've been doing a poor man's runout test by just rolling the cartridges on a mirror, but it's less than ideal (nor accurate) and I'm thinking about getting a concentricity gage from Sinclair.

[xrMike]

Is that the same as neck turning?

If YES, there was a recent article in that rifle magazine you get from the NRA where a guy did some testing re: the effects of neck-turning on group size. He was very surprised when his results showed there was no beneficial effect.

I can dig up the article and post more details if anybody's interested in his methods, etc.

(I don't have any real-world experience myself.)

[brando]

Eh, I'm not so into the idea of neck turning, but curious about making my bullet seating as uniform on axis as possible. Sure, that can involve neck turning, but I'm more interested in a good method of measuring how off axis a bullet is once seated. You know, that whole uniformity thing

[xrMike]

My bad, I'll shut up now...

[ar15barrels]

Is that the same as neck turning?

(I don't have any real-world experience myself.)

Neck turning has little to do with concentricity, even though tight necked chambers using neck-turned cases usually WILL show very good concentricity.

Neck turning is usually done to purposely THIN the brass to fit in a chamber than normal brass would NOT fit in.
This is benchrest territory for sure.

Turning necks on cases that will NOT be used in a tight chamber will not do anything for you.

Now, if you want the best concentricity, you should be looking at floating-chamber type seater dies such as Forester or Redding.
These types of dies align the bullet and the case BEFORE you start seating the bullet.
Traditional dies have the bullet just sitting on top of the case as you run the case into the die and rely only on the seating stem to align the bullet during seating.

[brando]

I've recently switched to a Redding Competition Seating die, so I think I'm already in line with what you're saying. So perhaps a Concentricity Gage wouldn't be much of an improvement?

[ar15barrels]

I've recently switched to a Redding Competition Seating die, so I think I'm already in line with what you're saying. So perhaps a Concentricity Gage wouldn't be much of an improvement?

A concentricity gauge is not going to make ANY difference to the ammo.
It's simply a measuring tool.

It will make a HUGE improvement in your ability to check the concentricity of your loaded ammo.
This would give you the ability to sort it into batches based on the readings.
Say you put all the 0.002" stuff in one pile and the 0.003"+ stuff aside for blasting.
THAT could make a significant improvement when it comes time to shoot groups for score (or beers).

[Rule .308]

A concentricity guage is a must in loading top quality ammo, how else do you know if your bullets are being seated correctly? The whole idea behind making the most accurate ammo you can is to remove all of the variables and make each round as identical to the next as you can. Neck turning not only makes it possible to fit a loaded round into a chamber with a tight neck but it makes sure that the brass in the neck area is of the exact same thickness. Think about it, if the brass is thicker and thinner in spots two things are going to happen, the neck tension from the brass will be greater where it is thicker and when the neck expands the brass that is thicker on one side can cause for a lop sided release of the bullet. If the brass is exactly the same thickness then neck tension will be more uniform as will the brass as it expands to release the bullet when the powder burns behind it and develops pressure.
I use a Redding micrometer seating die and it is very good, the other thing that I use that really reduced the runnout in my loaded rounds was to go to Lee collet sizing dies, good stuff for sure. The idea with the collet sizing die is that the neck is sized down against a mandrel that is perfectly centered. I will typically check my runnout on freshly sized brass as well as on loaded rounds so that I can monitor the runnout and if I pick some up at least I know at what stage in the process that I picked it up in. Another trick that works good on the collet sizing dies, and other sizers too I am sure, is to size the brass and then twist the brass in the shell holder and size it again. This helps quite a bit to minimalize the runnout.

Mark

[Mnort10x]

This is the answer!

http://www.bersin.info/

Great tool. Corrects runout problems.

[CSACANNONEER]

I've been debating on getting a Bersin. On onehand, it can help you adjust your run out down to .0005" or so. On the other hand, every time you adjust a round, you are changing the neck tension. I'm not sure which is more critical but, I'm thinking that uniform neck tension is.

[ar15barrels]

I've been debating on getting a Bersin. On onehand, it can help you adjust your run out down to .0005" or so. On the other hand, every time you adjust a round, you are changing the neck tension. I'm not sure which is more critical but, I'm thinking that uniform neck tension is.

The MOST critical thing is also the hardest to correct.
That would be the THROAT in the barrel.
If the throat is perfectly centered in the bore and it's no more than about 0.0002" oversize of the bullet, the bullet is going to be forced to align properly.
Unfortunately, MOST factory throats are upwards of 0.001" oversize of the bullet.
A throat this loose lets te bullet engrave into the lands crooked.
A crooked bullet throws off the balance and hence the accuracy too...

[PistolPete75]

Neck turning has little to do with concentricity, even though tight necked chambers using neck-turned cases usually WILL show very good concentricity.

Neck turning is usually done to purposely THIN the brass to fit in a chamber than normal brass would NOT fit in.
This is benchrest territory for sure.

Turning necks on cases that will NOT be used in a tight chamber will not do anything for you.

Now, if you want the best concentricity, you should be looking at floating-chamber type seater dies such as Forester or Redding.
These types of dies align the bullet and the case BEFORE you start seating the bullet.
Traditional dies have the bullet just sitting on top of the case as you run the case into the die and rely only on the seating stem to align the bullet during seating.

Is there a signficant result using these floating-chamber dies than the "standard" dies like Dillon for precision shooting? I'm thinking about getting competition dies for my .223 and .308

[ar15barrels]

Is there a signficant result using these floating-chamber dies than the "standard" dies like Dillon for precision shooting? I'm thinking about getting competition dies for my .223 and .308

You would have to have a concentricity gauge to check.
I never did compare standard to chamber seater dies.
I just went right to chamber seater dies from the start.
The whole idea behind them is just so much better in my mind.

[PistolPete75]

You would have to have a concentricity gauge to check.
I never did compare standard to chamber seater dies.
I just went right to chamber seater dies from the start.
The whole idea behind them is just so much better in my mind.

funny, there is always something to get in this fine hobby of shooting.