More about runout

[Poconolg]

How is runout corrected? I have a catalog from Sinclair. What is needed to check runout and what is needed to correct it? Is neck turning or correcting runout more important for accuracy? I am having a rifle built upon a Rem 700 receiver. I am getting a Lilja 26" barrel 1 1/8 in diameter with a Jewel trigger in 22-250 with a 1 in 14 twist. I will be shooting at 100 yds and am looking for 1/2" groups. Redding comp bushing dies and weighing each charge. Thanks for the answers on the previous thread.

[Poconolg]

I will be using new Lapua brass with a variety of match bullets; Berger, sierra Nosler

[Unclenick]

Redding Competition Seating Die helps. (Be sure to disassemble and clean thickened oil and re-assemble before use.) If you actually want to straighten a bent one, both the Bersin and Hornady gauges have a thumb screw that makes the effort, but I've heard mixed reviews of how effective that is. NECO has a bending jig you can use by trial and error. I have a block of steel (small stamping die blank) I drilled and reamed caliber sized holes in that seems to work.

Best policy is not to make eccentric ammo in the first place. Pick your Redding die bushings to size your brass correctly without an expander. Seat with the Redding seating die and you will see only a little runout due to neck wall thickness variation. You can outside turn or simply select cases to minimize that, depending on whether or not you can use the reject cases elsewhere for practice or plinking. Buy Lapua or Norma brass if you can afford it. I've never found more than a thousandth runout due to neck wall thickness variation in this stuff.

Per a recent thread, weighing each charge doesn't always work best due to water content variation. Has to have powder kept and loaded in fairly constant humidity conditions to produce consistent energy content.

[dahermit]

How is runout corrected?

That is the 64 thousand dollar question (or am I dating myself?). Having pursued the problem myself, I found, in my case that factory ammo shows minimum or no appreciable run-out out of the box as measured with a runout tool. Also, I found that in my rifle, the fired case had no apparent runout. It is the hand loaded rounds that had runout, indicating that it is induced during the handloading process. There is a great difference in dies, there can be a difference in the hardness from side-to-side in the neck of a case. There can be a difference in thickness in the different sides of the neck (corrected by turning the necks). Loading technique (chamfering the mouth, using boat tail bullets, etc.) can effect run out. Inasmuch as I no longer shoot rifle, I will leave the discussion to those who currently are pursuing the subject and maybe we both can learn something new.

[dahermit]

Best policy is not to make concentric ammo in the first place.

I am sure he meant: "Best policy is to make concentric ammo in the first place.

[Unclenick]

Yep. Almost. Meant "eccentric". I'll fix it. Thanks for the catch.

Interesting. I've measured 0.006" runout in commercial ammo, with 0.004" being common. That's corresponds to 0.003" and 0.002" of neck wall thickness variation, respectively, which a lot of brass has. The plus side for commercial ammo is the case is straight when they start. A lot of what give handloads extra runout is people pull the case necks off axis with the expanders in their dies. I've found the little near-spherical carbide expanders cause less of this, but I've also read an author who claimed they made it worse for him. I got one of the Sinclair mandrel die bodies and found that if I put an undersized expander in a die (still large enough to iron out case mouth dents) that doesn't drag on the neck, then expand with the mandrel in a second operation, this cuts way down on the problem. Even better is sizing the neck on a Lee Collet Die, then sizing the body with a Redding body die. That not only keeps a straight neck, but, due to the mandrel, prevent "the dreaded doughnut" from forming inside at the shoulder and neck junction.

[Poconolg]

The dies that I will be using are the bushing dies without an expander. What tools does Sinclair sell that are the best to check runout? It sounds like neck turning will reduce runout, am I correct?

[jwrowland77]

The Hornady Concentricity Gauge works pretty well. When I do have some over .003" runout, I use my Concentricity gauge and it works great.

[Clark]

~90% of bullet tilt [eccentricity] can be eliminated by not using an expander ball in the same step as neck resizing.

Once an expander ball has bent the neck, the best thing to do is fire the case again in the nice concentric rifle chamber. Neck straightening schemes never last long with me.

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Chasing that last 10% would take a sliding sleeve seater die, turned necks, tight neck chamber, and probably other subtleties beyond me right now.

One can avoid the turned necks by using the Lee Collet neck die that sizes with respect to the inside of the neck, not the outside. It also does not drag a big expander ball through a newly resized overly tiny neck.

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http://www.sinclairintl.com/.aspx/li...-_-Custom+Link

http://www.thehighroad.org/showthread.php?t=617604

https://www.ar15.com/media/viewFile.html?i=20782

http://thefiringline.com/forums/showthread.php?t=548430

"The NRA Handloader's Guide" 1969, a compilation from "The American Rifleman" 1950 to 1968, article gauging bullet tilt, by A.A. Abbatiello and was based on "The Bullet's Flight" by Dr F.W. Mann and the work of George L. Jacobson of the Frankford Arsenal in 1959:
"Mathematical Solution
The laterally displaced center of gravity moves though the bore in a helical (screw) path. The pitch of this helix is the pitch of the rifling, and the radius is the lateral displacement of the center of gravity. On leaving the muzzle the center of gravity continues in the direction it had at that point. .. The angle of emergence is that angle who's tangent is 2pi times the lateral displacement times the pitch. For a .004" displacement and a 10" rifling pitch, the tangent is 1/8 (2 pi)(.004) / 10 and the corresponding angle is 1.1 minutes.

...The effects which Jacobson found.. are essentially in agreement with the work reported here."

[Unclenick]

Originally Posted by Poconolg

It sounds like neck turning will reduce runout, am I correct?

It will reduce the portion contributed by neck wall runout, but it does nothing for a bullet that didn't start out straight during seating. The Redding Competition Seating Die will, though.

The drawback to turning necks is the thinner brass expands and is resized more, so it work hardens a little faster and needs annealing sooner. Glen Zediker recommends just turning enough brass off to touch 2/3 of the neck surface of a case with much neck wall runout. That's enough to help centering, is the idea.

[condor bravo]

When getting a concentricity gage, note that some require a pilot for each caliber while others do not. When you get set up you might want to try doing this. Separate the run-out variations into categories like .000 to .002, .003 to .005, and .006 and higher and then fire the various groupings for grouping on target to see if there is any noticeable difference. To refine this some, after measuring use a marker pen and mark the high spot (or low spot) of the run-out on the case rim. Then chamber each round with the mark oriented the same way, like at the 12:00 o'clock position. I did this using quite a number of different calibers and standard Mdl 70 and 700 sporter rifles. A disappointing exercise ending in frustration. Overall with just a few exceptions due to chance, there was really no differences between the .001 run-outs and the .007s and higher. But with a highly tuned rifle, better results might be forthcoming with this experiment.

[hooligan1]

Unclenick, how does th Redding die compare to the Forster Bench rest seating die?

[cw308]

I have tried the Redding S Type bushing dies to see if neck tension was more accurate, what l found was my original F/L RCBS die gave me a .001 & better runout. I used the Hornady concentricity gauge to correct runout when using the Redding S Type bushing dies. With your 700 head space is set to a minimum .001 With your setup you will get a .50 group at 200 yards, what will your trigger be set at. I'm shooting a trued 700 308 cal. Rock Creek M24 5R 11.27 twist HSPrecision bedded stock torque setting 65" lbs. Jewell trigger set at 10 ounces. Most of my friends have them set at 2. Just love shooting it. Good luck with yours.

[Unclenick]

Hooligan,

The Forster patent on the sliding sleeve was filed in 1969 and expired in 1989. In 1989, Redding (who'd been prepared), shortly after the Forster patent's expiration, filed for a new patent that combined the sliding sleeve with a floating seater stem (patent law allows for patenting new combinations of old things). The Forster uses a fixed seater stem. The Redding patent describes a situation in which the fixed stem can fail to align a bullet as well as the floating stem does. I have no idea how frequently that would really occur. What I can say is, I bought my first Redding Competition Seater (.30-06) right about 1990-91 after seeing an ad in Precision Shooting magazine. I was unaware of the original version by Forster at the time. But the Redding worked so well, cutting my runout by about a factor of 4, that I've never looked back. So I just don't know how well the Forster actually compares in testing.

Ironically, my concentricity measuring tool at the time was made by Forster/Bonanza.


Poconolg,

This is Sinclair's tool. No special supports required by caliber. Has a good reputation. The NECO case gauge with an extra V block will make measurements the same way as well as several more that I find useful, but it has a higher price tag.

[hooligan1]

Thank you fine sir...Now I will have to pick those up.

[jwrowland77]

I've been looking at that Neco Case Gauge to test wall thickness.

[F. Guffey]

How is runout corrected?

Run-out can be an illusion. the die can do as magnificent job of sizing the case. The bullet after seating can have zero run out but the neck can have an indicated run-put on the neck because the neck is not the same thickness all the way round it.

F. Guffey

[Unclenick]

Mr. Guffey makes a good point. You can have the bullet tilted a little so that by the time it gets to the tip from the neck, it will have no runout left even though it is eccentric where it meets the case mouth due to that neck wall thickness error. This bullet will look straight if rotated at the case and measured at the case, and also look straight when measured at the tip of the bullet by any of the available gauge types. You need to measure both at the bullet tip and at the bullet surface next to the case mouth and have both give you zero runout before you know you have a perfectly concentric cartridge.

The objective is to make the cartridge so that when it is driven forward to the headspacing surface by the firing pin, the bullet winds up centered in the chamber neck and coaxial with the bore until the rising gas pressure starts moving it. That's what prevents the bullet's center of gravity from winding up off-center with the bore, spinning eccentrically, and thereby lobbing the bullet into a radial drift at exit.

[Poconolg]

will neck turning solve some of the problem ?

[1100 tac]

I use a custom honed Forster size die with a custom made by me expander plug. the expander has only .0005 worth of work to do and I let it float by using an O ring on the stem between the lock nut and the die body. I seat with a Forster micrometer die in a Forster press, I use mostly Lapua cases for precision work and my runout is only what is to be found in the case or bullet itself. usually .001-.002. I'm thinking about trying the mandrel technique, but I would use my Forster to do it

At this point, I am not neck turning.

[F. Guffey]

At this point, I am not neck turning.

I am not neck turning, if anything I ream. When forming cases I make donuts, not when firing but when forming. Some of the donuts I make 'almost' close off the neck. Then there are reamer dies, not a new ideal. R. Lee had target model dies, my opinion? The reamer was worth the price of the kit.

F. Guffey

[cw308]

The Hornady gauge will correct runout.

[flashhole]

Screen/cull your brass. If you start out non-concentric you will not improve much, if any, in your processing. Yes, neck turning can uniform the necks of those that are lopsided but the center-line of the neck needs to be in the correct place to begin with.

Fire-forming then re-processing can lessen the culls but will not salvage all of them.

Brass that starts out concentric tends to stay concentric unless you have a flawed chamber.

You will do lots of measuring to get where you want to be.

[condor bravo]

I think flashhole is saying to use the runout tool on the case necks first and concentrate on those that are the most concentric. Outside neck turning will lessen the neck diameter some, and bullet tension as well, that could be of some consideration. If I were undertaking your project, before neck turning or inside reaming, by using the competition die sets I would first see how little runout can be achieved by that alone (as well as checking case necks for minimal runout to start with). If you can then achieve a majority of rounds with .003 runout or better, that may suffice without case neck turning. The only time I tried something similar to this was with mostly standard dies and used with sporter Mdl 70 and 700 rifles of various calibers, but accuracy improvements, even with .003 or better runout, were not particularly good. But possibly so with a tuned rifle. I did acquire some inside neck reamers but quickly gave up on that due to case neck thinning.