Accuracy One or 21st Century

[SteveOak]

I am looking to get either an Accuracy One or 21st Century concentricity gauge for the express purpose of measuring bullets to determine their deviation from being round. I have narrowed it down to the Accuracy One and the 21st Century.

I would appreciate input from those that own or have used one or the other or best case, both. Specifically why would you recommend one over the other?

I am interested in roundness rather than concentricity as the bullets I will be measuring are monolithic.

Either one is affordable so that would not be a consideration. Usability, precision and accuracy are the important considerations. Please suggest other relevant considerations.

Does the separate, smaller wheel on the Accuracy One contribute to accuracy and/or precision?

 

[BenPerfected]

Steve,
What is the difference between roundness and concentricity? What you are looking for is consistency. IMO, the Accuracy One gauge is excellent.
Ben

 

[SteveOak]

I understand concentricity to be the relationship of the bore axis of two circles. Here is what I think of when discussing concentricity.

So the relationship of the outside diameter of the bullet at the base compared to the outside diameter of the mid point of the bullet would be concentricity, I don't think that either device would measure that.

Thank you for your response. I am looking more for the basis of your opinion that the Accuracy One is excellent in order to decide on one rather than the other.

 

[mikecr]

On terms, you're lost as a nine-eyed dog.
You don't measure 'bullets' with either tool. What you measure with them is total indicated runout (TIR) of either brass cases at the necks, or loaded cartridges off bullet bearing forward of case mouths.
The only tool measuring 'bullet roundness' (loosely) is a Vern Juenke ICC.

Forget concentricity. Straight ammo measures low in loaded TIR (the best you can do).
Straight ammo shows low eccentricity, but concentric ammo might not be straight at all.
If TIR is what you're looking to measure then IMO the Accuracy One is best.
The wheel doesn't make it better, but it's a nice feature.

 

[SteveOak]

On terms, you're lost as a nine-eyed dog.
You don't measure 'bullets' with either tool. What you measure with them is total indicated runout (TIR) of either brass cases at the necks, or loaded cartridges off bullet bearing forward of case mouths.
The only tool measuring 'bullet roundness' (loosely) is a Vern Juenke ICC.

Forget concentricity. Straight ammo measures low in loaded TIR (the best you can do).
Straight ammo shows low eccentricity, but concentric ammo might not be straight at all.
If TIR is what you're looking to measure then IMO the Accuracy One is best.
The wheel doesn't make it better, but it's a nice feature.

You are quite mistaken on several points.

This effort is for bullets, not loaded cartridges.

Furthermore a Vern Juenke ICC does not "measure" bullets it only compares one bullet to a reference. The output units are "deviation units" not fractions of an inch or millimeters.

 

[mikecr]

What you're measuring in the picture is deviation -of combined boat tail base & bearing variance from 'round'.
You're not measuring eccentricity, but searching for centerline via subtraction of runout. This seems not the same, as actual eccentricity measure established from expected centerline axis, end to end. After all, if it can be out of round, it can be a banana end to end.

I concede that I've never seen a standard runout gauge used for bullets, and I'm not sure what would cause a bullet to finish out of round. But once you fire a bullet through a bore, it may take a shape a bit out of round, or departing from your measure. This IMO would leave your described measure void of validating on target.
I know a Juenke will show out of round condition(good as and no better than an indicated v-block) as well as jacket thickness variance. I can understand how jacket thickness would affect mass centerline, or eccentricity of mass.

I did think you were after straight ammo, and the tools mentioned are really useful for that. So all I should say further is good luck with your endeavor.

 

[Endyo]

The Accuracy One tool is probably the best of the "concentricity gauges" on the market.

They both offer the large turning wheel. I really like John and his products so it's hard not to recommend the 21st Century products.

Since you mentioned price is not a factor I would opt for the more expensive Accuracy One.

I don't believe either will be more of less accurate than the other. User error is mostly eliminated by the turning wheel. Get a quality indicator and you should be set.

 

[R.Morehouse]

If your loaded round is showing run out and your measuring device doesn't allow you to nudge the run out ( bullet ) to make it straighter according to your indicator, don't you think the device is lacking in what could be considered a critical way?......Just Sayin'

 

[Endyo]

The OP is wanting to measure the actual projectile (bullet). Not the loaded round (cartridge).

There is a lot of debate on bullet straightening. Some claim it pushes the R/O further down the case body only temporarily solving the problem. Some people swear groups shrink. I can't tell.

For simply measuring the projectile I think either two will work with the (slight) edge going to Accuracy One.