21st Century Concentricity Tool

nksmfamjp

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Joined
Jan 5, 2004
Messages
1,155
Any thoughts on this? It it a good tool? Easy to get repeatable measurements on?

I’m hoping to step up from my rcbs Case Master. The only negative is that the RCBS will tell me neck thickness as well as neck thickness variation. I could get another tool for that, I guess.
 

squeeeeze

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May 21, 2011
Messages
388
Location
Arizona
I have the 21st Century with the wheel. The wheel is a little finicky as it wants to spin the case forward or backwards. I usually adjust so it spins back against the stop. The O ring rotted quickly and have had to replace a few times. Make sure to get spares, or try it first without the wheel as it’s not really necessary. The gauge for me is finicky also. You can’t just have it 90* and the gauge isn’t as easy or quick to setup as my Sinclair was.

I bought this to replace my Sinclair Concentricity tool (similar setup as yours’ without the ability to measure neck thickness) and to be honest I liked it better and was easier to use. I honestly regretted selling the Sinclair. I like the best products and gadgets myself so I had to have the 21st. While it does work and accurate, just not as user friendly as the Sinclair I had at half the price. It very well could just be me though.

As stated you’ll have to buy a separate ball micrometer to measure neck thickness. I like my Hollands 3rd hand and makes things much easier then trying to fumble.
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Last edited:

Howland

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Nov 19, 2017
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89
Location
Upstate SC
I have the 21st Century tool with the wheel. Yes you have to set the wheel slightly offset to 90° to avoid the case moving forward. It's a nice tool and worth the money.

I measured in the middle of the neck and a point halfway between the ogive and tip. Neck concentricity showed 0 to 0.0015" out of round, about the same as measured neck wall thickness. Bullets showed 0 to 0.0085" variation, or 0.00425" TIR. This clearly points to the seating process as inducing runout.

I sorted 50 measured rounds by runout, best (almost none) to worst, and the worst shot a slightly smaller group than the almost none.

The concentricity tester now sits on a shelf collecting dust until I improve my fundamentals enough so the variation induced by the nut that holds the trigger has been reduced enough so it no longer obscures the other sources of variation (loading process, tools and components).

It was worth the price to confirm that. I had thought I was a pretty good shooter but needed more expensive reloading gear. Looking at it from that perspective, it saved me money.
 

Beluebow

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Joined
Dec 6, 2004
Messages
254
Location
Ar.
The 21st century is a nice tool.....that said concentricity is way over rated IMO...modern day quality components and dies will typically keep runout at tolerable levels.
 

Mikecr

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Joined
Aug 10, 2003
Messages
5,600
Location
NC, oceanfront
There are a couple things important with this;

1. Forget concentricity and don't subtract or cheat from your raw readings. Total indicated runout is just that.
There is a lot more to it than necks, or bullet seating. These V-Block gauges show all deviation FROM STRAIGHT.
When you make straight ammo, it is low in TIR, and if it helps you sleep that is also low in concentricity as well.
Keep in mind, a cinder block can be centered up concentric between 2 points, but it is not straight. It would not chamber well in a cylinder. Think no runout = dead straight = best you can do.

2. Runout matters only when exceeding chamber clearances. The reason it matters then is because it sets up chambered pressure points. You may think then that sloppy clearances are the way to go -except it is sloppy clearances and all the sizing needed from this, that leads to higher runout.
Either direction tight or loose are circles feeding on themselves. One circle is big, one small, both just fine the way they are.
You can have big runout in a sloppy chamber that created it and doesn't punish you about it.
You can have very little runout in a tighter chamber that produces less runout, and all is great there too.
 

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