Concentricity (Bullet Runout)

[Kjb1796]

What is your "go"/"no go" number?
How much bullet runout is acceptable for your competition load?

Thanks

 

[cp3head]

I will be interested to see what everyone has to say regarding this topic as this is something that I have been looking at also. What concentricity gauge are you using?

 

[LC Tikka]

Get the bullet run-out as low as possible always.
Turn the case neck to uniform thickness, load and fire then measure the case neck run-out to assess the chamber "concentricity". One is no good without the other!!
LC

 

[dkhunt14]

I'll go first. I quit measuring it quite some time ago. So there isn't a "no go" for me.

Tom

I stopped measuring along time ago. I got it out the other day to measure something else and it sat so long the dust froze the stem fast on the dial indicator. I don't think it is as important as other things. Matt

 

[Patch700]

I'll go first. I quit measuring it quite some time ago. So there isn't a "no go" for me.

Tom

I stopped measuring along time ago. I got it out the other day to measure something else and it sat so long the dust froze the stem fast on the dial indicator. I don't think it is as important as other things. Matt

Same here.. I turn necks to try to attain a uniform bullet grip and release.. As far as concentricity goes I think IF measured properly it can be used as a gauge to pinpoint if you have a problem in the resizing operation ...

Some swear by it and others put too much faith in it.. If it makes you shoot better then by all means .

The best place to start is with quality components and tools..

 

[Kjb1796]

I have an RCBS & was considering one from 21st Century.
I don't remember where I saw it, but it seems like someone said that if run out was over 6ths then that round went in the fouler box.

I never thought about checking the fired case necks for run out.
I have a pile of once fired brass I can check.

At the moment I'm shooting a stock rifle in .308 FTR using factory match ammo and trying to reduce the where the HECK did that come from impacts.

I will be reloading again for this rifle. I've never turned case necks but I plan too.

 

[jonbearman]

Go to you tube for many videos on neck turning and I like a 21st century model a. It is beefy and the adjustment is solid.

 

[ZenOhSix]

For those shooting .308 - what type of brass and wall thickness are you trimming down to? I have seen some people measure a few different lots of brass, pick the average, and subtract .002 or .003; then they turn all brass to that value. I have also seen people pick an arbitrary number that falls in that general range, i.e. .0125 wall thickness and trim everything to that.

I am at the point of trimming now - and I am not sure which method is best. I have both Lapua (brand new) and once fired Federal Gold Medal Match brass.

Thanks,
Mike

 

[jr600yd]

Mike,
First sort your brass by headstamp.
Second measure neck wall thickness by brand. You'll find differences in brands as well as lots. Third set your trimmer up for one lot of brass and turn those. You'll probably have to readjust the turner for each group. Keep them seperate from each other. One group is not better than another but you'll find consistency within each group much better than if you mix them up. You haven't said what chamber you have but if it's a standard SAMI you won't be turning much off the case. Probably 1/3 to 1/2 the case neck, just enough to clean the neck up.

Why turn at all?
If you have a tight necked chamber you must neck turn. If not what is your reasoning for neck turning?
Many believe neck turning improves accuracy but is it true? In a standard chamber you may be just increasing the "slop" between chamber and case.
All cases are banana shaped to some degree. Some believe when the round is fired the thin side of the neck releases the bullet before the thick side, hense the bullet is a little off center when entering the lands and groves. Neck turning makes the whole neck even and allows 360 degree release of the bullet. (Sounds good hummmmm)
Others believe the real reason to neck turn is it improves the life of your brass. There is a little more room between the neck and the die thus your not working the brass as much. We have all had the experience of removing a case from the sizing die and having to give the press handle a good bump to extract the case. Neck turning, just taking as little as .005 off makers sizing much easier.

Concentricity: there are several good tools on the market to measure concentricity. I use the NECO.
Years ago I did a test to see if it had anything to do with accuracy. Granted I'm not a bench rest shooter, I shoot highpower. Shooting at 600 yds I found for my type of shooting runout up to .005 had no impact on scores or POI when you consider all the other variables involved. Past 600yds or runout over .005 did. Now for my long range ammo (800 - 1K) I keep runout to .002 or less.

So what it comes down to is "is it worth it?"
If your a bench rest shooter or have a tight neck chamber YES!
If your shooting a standard chamber or competing at ranges 600 yds or less NO!

Case trimming length. I've always trimmed to the recommended length. (2.005) and again when the brass reaches max length (2.015) never had a problem. Personally I don't believe that .010 change effects accuracy at all.

 

[Down South]

I'll go first. I quit measuring it quite some time ago. So there isn't a "no go" for me.

Tom

+1.........Same here.

 

[BoydAllen]

For me, concentricity gauges are best used to diagnose die problems. The primary culprit is the sizing die, BUT a sloppy seater can degrade concentricity as well. For general use, on cases and ammo, the Sinclair unit is very good. It can be adjusted over a wide range, and has very good roll friction, or rather lack thereof. For me, those are the main issues by which I evaluate a design. If for some reason you want to trade case gauging for ammo straightening, the H&H is excellent. I would avoid the RCBS because of case support friction issues, and the Hornady because rims are not concentric with case bodies after firing, and it is the parts that contact the chamber that we need to be concerned with. I own several concentricity gauges, and have reviewed several more than that. Case friction and adjustablility .....

 

[mikecr]

I haven't run a scientific test on it, but I suspect loaded runout matters where clearances are tight.
And with this, I suspect that common dismissal of runout leads many to discover improved results with loose clearances.

I run one chamber(a personal test gun) that's tight across the board. Necks are fitted.
For this my cutoff is 1thou TIR measured off bullet bearing with a Sinclair unit Boyd mentioned. Any more than this and I already know there would be chambered tensions, and IMO, that can't be 'good' for results.
I see chambered tensions same as other tensions(action, trigger guard, stock) we might put on a gun(like a thumb on the tang). In other words, possibly contributing to flyers.

I'm not suggesting<.001 TIR is at all normal,, just an example in contrast to "I quit".
It can easily be done. I can load straight with any of my chambers w/custom dies.

On the flip side, if your ammo fits like a rat turd in a violin case, it would take a helluvalot of runout to matter.
Right? It makes sense to me anyway.
But I would still throw out any >3thou TIR. It's just ridiculous and something's broke by then..

As far as runout measure, I believe the v-block type is best, as it's least forgiving(your ammo is straight or it isn't). I do not support neck-benders.
Mine: http://www.sinclairintl.com/reloading-equipment/measuring-tools/concentricity-gauges/sinclair-concentricity-gauge-prod37479.aspx
What I think is best: http://www.accurateshooter.com/gear-reviews/new-wheel-drive-concentricity-gauge/
M

 

[Raythemanroe]

My opinion is you check your setup and leave it alone. What I mean is if your not producing bad brass and your within tolerances you find acceptable then your good to go.. I don't find much use for it other then diagnosing problems in your setup.. I concentrate on measuring bullets and seating depth..


Ray

 

[ZenOhSix]

Mike,
First sort your brass by headstamp.
Second measure neck wall thickness by brand. You'll find differences in brands as well as lots. Third set your trimmer up for one lot of brass and turn those. You'll probably have to readjust the turner for each group. Keep them seperate from each other. One group is not better than another but you'll find consistency within each group much better than if you mix them up. You haven't said what chamber you have but if it's a standard SAMI you won't be turning much off the case. Probably 1/3 to 1/2 the case neck, just enough to clean the neck up.

Why turn at all?
If you have a tight necked chamber you must neck turn. If not what is your reasoning for neck turning?
Many believe neck turning improves accuracy but is it true? In a standard chamber you may be just increasing the "slop" between chamber and case.
All cases are banana shaped to some degree. Some believe when the round is fired the thin side of the neck releases the bullet before the thick side, hense the bullet is a little off center when entering the lands and groves. Neck turning makes the whole neck even and allows 360 degree release of the bullet. (Sounds good hummmmm)
Others believe the real reason to neck turn is it improves the life of your brass. There is a little more room between the neck and the die thus your not working the brass as much. We have all had the experience of removing a case from the sizing die and having to give the press handle a good bump to extract the case. Neck turning, just taking as little as .005 off makers sizing much easier.

Concentricity: there are several good tools on the market to measure concentricity. I use the NECO.
Years ago I did a test to see if it had anything to do with accuracy. Granted I'm not a bench rest shooter, I shoot highpower. Shooting at 600 yds I found for my type of shooting runout up to .005 had no impact on scores or POI when you consider all the other variables involved. Past 600yds or runout over .005 did. Now for my long range ammo (800 - 1K) I keep runout to .002 or less.

So what it comes down to is "is it worth it?"
If your a bench rest shooter or have a tight neck chamber YES!
If your shooting a standard chamber or competing at ranges 600 yds or less NO!

Case trimming length. I've always trimmed to the recommended length. (2.005) and again when the brass reaches max length (2.015) never had a problem. Personally I don't believe that .010 change effects accuracy at all.

Thank you for your insight and advice! The gears and cogs are turning in my head a little more now.

Honestly, I was turning because it was supposed to increase consistency (neck tension), which was supposed to translate into improved accuracy. It was more of a "follow the crowd" sort of thing, rather than applying specific shooting style and factors into the equation.

Which, I am not shooting Bench Rest - but rather Prone/Bench at 100 to 600 yard ranges (primarily 100-300, unless I do an F-Class match which can go out to the 500/600 yard distance); this is done via a Harris BiPod and a small rear monopod or sandbag.

In regards to the tool that you use, thank you for that recommendation. I had previously already purchased a Sinclair Digital Concentricity unit.

Else, thank you for your advice. It is extremely helpful as it applies to the type of shooting that I am doing, along with your results for the return of investment!

Sincerely,
Mike

 

[jr600yd]

Mike,
Just a little tip to make straighter more concentric ammo. When you seat the bullet only seat it 1/3 of the way. Turn the case in the shell holder 1/3 turn and seat the bullet 1/3 ( now seated 2/3 of the way) turn the case another 1/3 and seat to length. This works with turned or unturned cases. It allows the bullet and case to find there center in the die.

 

[bigedp51]

The military standard is .003 or below neck runout for match grade ammo.

 

[BoydAllen]

For those that want to know something about loaded round runout affects accuracy, I would recommend an article in a book, published by the NRA, titled Handloading. In it (Jan. '81 edition) there is an article on pages 86 and 87 by AA Abbatiello that discusses the subject based on actual tests (not on the basis of "It makes sense to me.") The article makes reference to tests that were done using service and match ammunition loaded with .30 cal. 173 gr. BT bulllets. There is a graph showing bullet tilt data which correlates group enlargement. It also shows how tilt was measured. The test referred to was performed by George L. Jacobsen of Frankford Arsenel, who collaborated with the writer at the 1859 National Matches who then wrote an article titled ".30-06 Cartridge Cases and Accuracy" that appeared in the January 1960 edition of The American Rifleman.

Cutting to the chase, the graph shows the amount that various amounts of bullet tilt increase group size, running between 1/4 MOA for .001 tilt, to what looks like 1 1/4 MOA for .005. The peaks of the curves (representing greatest frequency) were .002 for match, and a little over .0025 for service.

What is my point? Guessing is not the way to solve these problems. Bullet tilt matters, it effect can be predicted using mathematics, and actual tests have been done.

 

[ZenOhSix]

.. {snip}
Cutting to the chase, the graph shows the amount that various amounts of bullet tilt increase group size, running between 1/4 MOA for .001 tilt, to what looks like 1 1/4 MOA for .005. The peaks of the curves (representing greatest frequency) were .002 for match, and a little over .0025 for service.

What is my point? Guessing is not the way to solve these problems. Bullet tilt matters, it effect can be predicted using mathematics, and actual tests have been done.

That is extremely helpful.

Two questions:

1) Do you have a master list of Tips cataloged somewhere, referencing articles like this? Or was this a google hit and you just quoted the article you found it in (didn't seem like that was the situation here...)? Else, how would someone like I find that information (outside of coming across you or others in this forum post)?

2) Outside of what has been mentioned in this thread, using the gauges, etc. - is there anything else that should be in the process that hasn't been mentioned?

Thank you!
Mike

 

[BoydAllen]

I have the book. If you want the straightest possible brass with turned necks, a one piece die that is matched to a chamber that is matched to your brass is IMO the best approach. This is a rather complicated subject and I do not particularly want to write a book on the internet to properly cover, but if you PM me, we may be able to get something done about it. On the seating side, there are smiths that will build you a custom arbor press seater using your chamber reamer. Beyond that, there are some refinements of how the actual seating is done that can help. I believe that at least one has been mentioned in this thread. I should mention one more thing. It is common for shooters to focus in on one or two details, that may be inconsequential given their inattention to others that are more important. Accuracy is a weakest link thing. Make sure that you really know what your weakest links are, and have not simply chosen to blow them off as inconvenient.

 

['Freak]

You’ll find plenty good reading here: http://riflemansjournal.blogspot.com/

Get a copy of “Handloading for Competition” by Glen D. Zediker

Don’t overlook the AccurateShooter.com “Bulletin” and “Articles” at the top of the page.