Home Forums Hunting & Shooting Ask The Gunwriters Down the Bunny Hole of Concentricity

I want to thank this forum and specifically Follically Challenged and Mule Deer for my Christmas present.

KYHillChick told me she was stuck for a gift for me, and sent me looking. I was on Natchez Shooters Supply and found a Hornady Concentricity Tool for about 40% off normal street price.

I want to thank Folically Challenged. We were discussing runout on the way back from our Georgia Hog Hunting trip (Lord knows we didn't have much to talk about re: the hogs) . He's what got me thinking about it. I also want to thank Mule Deer for the original impetus.

Yes, I know the Hornady tool isn't the best, but it's a start.

Here's my weblog entry:

Hornady Concentricity Tool

I also want to thank KYHillChick for keeping me in reloading gadgets for the last 20 years.

Update: I went home this evening and measured and adjusted 25 rounds of the 8X57 Mauser rounds in about 15 minutes.

Overall, this batch wasn't too bad. There was one flyer that went .006 the rest started in the .001 to 003 range. Even the worst one needed only two tweaks with the adjuster to get it into the sub-.001 range. So far I'm impressed. I know y'all are kind of down on the Hornady. What am I missing?

KyHillChick sounds almost too good!

The Hornady works great for measuring run-out, and also for relatively small tweaks of run-out, say .003 or so. But more than that often means the bullet "pull" is loosened a little, because it's tilted inside the neck--which isn't tilted along with the bullet. Which is why I prefer the Tru-Angle tool for straightening loaded rounds: It bends the neck along with the bullet inside.

That said, if runout is over about .005, even the Tru-Angle doesn't totally fix things, because of brass problems.

If you keep this up you will run out of excuses for those bad shots.

I use the Hornady tool for the express purpose of checking the runout on my handloads to ensure that all is well; it works just fine for that purpose.

Generally if you are less than .004" TIR, you'll be golden, unless you are shooting camp Perry or some other form of competition. Also, if your dies are not making straight ammo, you likely dont have them set up properly. I have all of my run of the mill RCBS dies set up to produce. 003 and less TIR. This is one of my main uses for a good concentricity gauge.

You're right. I try to optimize my loads for plausible deniability. For instance, I stick with standard cup and core bullets ( mostly Hornady IL's) so that if I need to come up with an excuse, I always have bullet failure readily at hand. Also, most of my deer rifles have Bushnell Banner scopes on them. It's hard to fault a guy outfitted so.

Regarding Plausible Deniability

I learned this tactic on this very august forum.

After over 20 years of marriage to my hillbilly woman, the only downside I have found is I need to get her across the bridge on a frequent basis so that she can wiggle her toes in the Kentucky Bluegrass or else she has a tendency to turn into a wildcat.



OK. I can grok that. That might also explain why the couple of odd ones that had the most runout also were the ones that I could not adjust completely. The best I could manage with them was about .002" .

Two questions Mule Deer:
1) I looked up the Tru-Angle tool. It looks similar to something I cobbled up out of hard maple to accomplish the same thing. But I made my holes "bullet diameter" Based on what you wrote about bending the neck and the bullet, I am guessing the Tru-Angle tool's holes are drilled to "outside neck diameter." Is this correct?
2) When I spin a case on my concentricity gauge and the needle moves through a total swing of .004", do we call this ".004 runout" (the total measured deviation) or ".002 runout?" (the bullet's deviation from the longitutional axis of the loaded round). I think it's more than semantics since we are talking about what is or is not important and I want to speak the right language. When you say .005" above, which of these two ways do you mean that?

Thanks,
Rex

P.S. I of course welcome answers by anyone who knows them, not just JB.

Generally it's total needle swing in these conversations.

Good for you, Shaman!

I was lucky that the "Gack" book found its way to me relatively early in my reloading endeavors. I feel like it's saved me from lots of unnecesary trial + error.

FWIW, my personal level of accuracy seems to weather runout of roughly .003 or better. Beyond that, I feel comfortable blaming the ammo. A real revelation was checking loaded factory rounds: the ones that had always shot best for me were .003 or better, while some of the crappier stuff was frequently at .006, or even higher.

Have fun playing with it!

FC

I think several years ago I asked you a question about how straightened rounds compared to those that came out straight to begin with and your answer closely followed JB's.

Since then I use the ones that were more than .005 run out and straightened for foulers when I sight in or check my zero. Less than that, I have seen no difference in them when straightened. I am not a competition or long range shooter though. I use apiece of 2" x 2" x 1/4 " aluminum angle that I drill and reamed a row of holes across the top of one leg and clamp it to my loading bench when needed.The holes are a few thousandths in diameter over the neck diameter of the cartridges I load for.
What I don't understand is I how can run a 100 rounds thru the loading process with .001-.003 run out and have 5-6 that are .006-007. I assume it is the brass

Could be the brass. Check the necks with a tube mic and you may find the culprit.

Found the answer to half of my question!
Tru-Angle instructions

1 - outside neck diameter. To retain consistent neck tension, you want to move the whole neck by bending at the shoulder, rather than just tweaking the bullet by bending the neck.
2 - total needle swing. +/- .002" = .004" runout.

Or just get Forster dies and skip the bending part all together.

I agree. Fired cases extracted from a rifle's chamber are straight. 99.9% of the time. Runout is introduced by the dies. Although I am not brand loyal, in cases like this, if I absolutely, positively had to have (virtually) no runout, Forster would be my recommendation. I use Forster dies for several of my specialty rifles.

Update: I have mounted my tool on the bench and done some more testing. Pic and details here.

Update: Hornady Concentricity Tool


Big takeaway: Everything I test is pretty much good to go for hunting. Very little adjustment is necessary.

If that works for you, then all is good.

That has not been my experience. Unfired brass is generally about as straight as it's gonna get. Firing yields brass with some curve to it. It's not the chamber's fault, and the most perfect sizing dies have not been able to straighten the brass. The source of the curvature on the brass (that manifests as eccentricity, wobble or TIR on a case gauge) is the uneven thickness of the brass. On firing the brass doesn't want to stay straight when the walls are not the same around the circumference.

Smarter folk than I worked it out and laid out the path that showed me the value of Lapua brass (consistent wall thickness). Creighton Audette was not wrong. I always found it curious when my friends at the AMU shared that they shot virgin brass at 600 and 1000 yards until I started doing some testing myself.