6.5 creedmoor brass concentricity

[Scott_B]

Robert,
Many here will show all kinds of tools and ways to measure concentricity. The bottom line is concentricity is a bi-product of good brass prep, not a goal. I made this video to explain that and a few related things.

By the way the Hornady concentricity gauge is a real POS, and that's from someone who likes many of the Hornady tools.

Good luck,

Joe

As some one who has the Hornady POS, what do you recommend instead?

 

[Robert Robinson]

Scott

The POS, it’s a well made product but the idea of pushing a loaded round until its straight just didnt work very well for me. My prairie dog rounds were loaded with a moderate amount of neck tension. That means I could put the bullet tip on the table and push it in with a moderate amount of force(15lbs?). Rifle is a single feed no mag. After forcing the loaded round to a somewhat more concentric line sometimes the bullet would fall back in the case under the spring tension of the tool, nearly nothing.

So now its only used for checking concentricity. I made a mandrel so I could measure unloaded brass as well. That brings up another question. Is the brass rim a good place to reference from? No question the neck is. Been experimenting with a piece of aluminum angle in my bench vice some dry lube, a mag base dial gauge from work that I use for alignments. There are several versions available, when I get one, it will be a multi function type. Guess I would say, don’t purchase the hornady.

 

[Robert Robinson]

ButchLambert

Yes I have taken measurements at all stages. My habit of index marking brass is useful for letting me know what isn’t the problem but sometimes leads me in the wrong direction. For example; lets say somebody set his seater die on the table and the inevitable happened. Focusing only on the die and its parts but not that aluminum lock ring. His press uses the upper surface of that lock ring which is now raised by a few thousands. Index mark is always aligned with lock ring split, occasionally rotated from that reference just to check things.

I guess it may boil down to the tool I use for taking the measurements. Experimenting with other ways usually puts the index in the same quadrant.

It’s a hobby. previously I did the best I could with a few thousand rounds, now it’s a few dozen.

 

[Robert Robinson]

OK guys, thanks for help breaking a bad habit. The hornady concentricity gauge no longer on the bench. Found the old 36” plate glass, put a pencil under one side and rolled em. Man those are straight bullets not a bit of wobble. However, turn the worst noslers around and its clear the rim is not center. Smoked a few fired ones and they appear to be a perfect fit.

Thanks for the input

 

[Scott_B]

If money is tight, I would encourage you to put the money towards good micrometers (inside and outside), a micrometer stand (can't get good reliable readings from trying to simultaneously hand hold a case and a micrometer), and calipers.

If the money is available and/or you're a tool junkie like me then, I do have the Accuracy 1 gauge shown below. But I bought that when I didn't know any better and was pursuing concentricity like many advocated. These days I occasionally/rarely use it because its a waste of time. Every time I check them is .001-.002. I'm not bragging, if you do the other stuff, its a natural outcome. Like 2+2=4

By the way, this the only correct way to measure brass runout. You could do it on the bullet bearing surface, but the runout could also be introduced by your seating die. Measuring runout on the outside of the case neck is analogous to examining the outside of the barrel to see how straight the bore is.

Kindest regards,

Joe

View attachment 1095273

Thanks for the advice. As I understand the excellent replies, I need to have a stationary reference on the inside of the case as I rotate the case. Hopefully some sort of output such as a analog dial or digital output.

Texas is nice, but I prefer were I is @. Warm but not Mojave Desert warm, no below 40 degree F temps. I r not as grammar nazi neither.

 

[Robert Robinson]

Hey Scott

I used the dial indicator and the adjustment rail from the hornady concentricity tool and made my own.
It has 2 plastic V shape rests, 1 just below the shoulder and the other riding on the webbing area, rotation is manual no fancy wheel but it gets the job done. I figure if your necks are uniform thick from turning and measure, then an outside neck measure is adequate. After bullet seating I adjust the tool and re measure runout. It is my belief at this moment (could change) that concentricity from the rim is not as important as the webbing. I also got an order of Peterson brass but that’s another subject.