Run out

[jelenko]

identified variables and tried to isolate and measure their impact

How do you do that without measuring the variable?

 

[mikecr]

Loaded TIR matters only when it exceeds your chamber clearances.

 

[dgeesaman]

1/8” is definitely too much.

How many is just enough? Nobody knows.

 

[jackieschmidt]

How do you do that without measuring the variable?

^^^^^^
I tend to worry about things I can do something about. When dealing with rifle performance, there seems to be infinite variables that can cause a bullet to take a different path to the target than what was intended.

Things we can actually measure and compare to a standard are easy. You have a baseline to figure out how to correct the anomaly. Being able to correct it is the big “if”.

You simply have yo decide if the correction is worth the effort.

 

[ronemus]

If the chamber is concentric to the bore(shapes sharing the same center) how does a few thousandth run out matter? And run out would be half the neck clearance after chambering?

My concern is that chambering a round with large runout will correct the bullet angle, but in the process it will alter the bullet pull force (by deforming the neck) which is known to affect performance.

 

[mikecr]

Runout as an issue isn't about bore alignment and/or neck tension, and that's easy to prove yourself.
You won't see affects of runout until the upper case presses with considerable force against it's chamber wall. Basically, when you chamber a banana, establishing an abstract pressure point.
On firing, that case snaps to unload one side and ping the other side, sending an offending vibration back & forth the length of the barrel. This is a problem because it's different than vibrations are otherwise.

Typically we can get away with around ~5thou TIR before seeing it on target.
That's a lot of runout, even for a sloppy chamber.
With a tight chamber (not just with necks), ~2thou can be a problem,, but tight chambers do not produce bananas. They produce very straight cases.
If you run a tight chamber and sloppy sizing,, enough to cause ~2thou TIR,, then you'll be reaching for a looser chamber -to shoot better.
This is part of why loose chambers seem more forgiving.

 

[ArtinNC]

I'm betting most Competitive shooters are using custom made dies that match their chamber . Not saying you have to have them ,but I'll bet top competors have them .

 

[Webster]

From my experience and testing.
No I did not run a half million tests in 47 barrels in 16 countries fired only by Swiss virgins!
Now that, that is out of the way.
If neck tension is a causal factor for accuracy in the discipline you shoot, then run-out of a loaded round is part of the puzzle. If neck tension is not "that big" of a consideration, then no worries for you.

If your loaded rounds are out just a tiny bit, then you are likely good. If they are out far enough to get straightened in your chamber, you could be changing the neck tension a tad when straightening the round?

Several years ago I asked the same question on this forum and received a multitude of answers. I actually was expecting the "guru's" to give me a unified and single answer. As an example, "X amount is problematic, less than that, no worries". That is not the answer I received and I set out to do some testing.
After ordering several sets of dies and using 3 different presses, and spending a plethora of time adjusting this and that......... I went to the range to test.

1.) Jumping bullets...... I just could not see a difference if less than .005" runout, however I did not test jumping very much.

2.) Jamming bullets, less that .003" you will very LIKELY have no worries. Less that .002" and you're golden. I tested this with actual die induced runout (the best a die and press could produce) and with intentional runout (me corrupting the system to make matters worse), and with rounds I buggered up making things worse. The worst case always shot like I was slightly out of tune. A .010" runout round nearly always landed out of the group.

NOTE:
This testing was done with a 6 Dasher at 600 yards.
It may have no value outside of that rifle and distance?

I have friends that check every round prior to a match and the straightest rounds are the record rounds. The banana shaped rounds are used for sighters and such. I built a system based on my testing and stick to it, but I check all the time. Unlike many folks on this forum, my concentricity gauge gets used plenty.


CW

I always thought that running down a 24" barrel and getting engraved by the rifling would straighten out a bullet. It's now concentric with the barrel. I wonder if getting straightened by the forcing cone or barrel rifling damages the bullet? I don't have to worry about this stuff because my rifles shoot under 0.500" with almost no load development.

 

[tharger]

Can't remember for sure but wasn't it Eric Cortina who made some rounds crooked on purpose and shot them and made no difference.
Don't remember by how much.

What can you do to make a round crooked on purpose?

 

[jackieschmidt]

What can you do to make a round crooked on purpose?

This little tool will do the job. You can get it as crooked as you want.

 

[Mulligan]

What can you do to make a round crooked on purpose?

This tool was designed to straighten ammo, however as you can imagine, you can make stuff wonky with it also.
CW

 

[Doug Casner]

Never tried to straighten a crooked neck. Ran millions of them on taper at L.C. Looked like a shotgun shell when the case got to taper. We put the neck on them hopefully straight. Little tricks you could do on taper to straighten them but I wouldnt know what to do with a crooked case after it made it to the loading bench. Just throw it away. Doug

 

[BoydAllen]

Never tried to straighten a crooked neck. Ran millions of them on taper at L.C. Looked like a shotgun shell when the case got to taper. We put the neck on them hopefully straight. Little tricks you could do on taper to straighten them but I wouldnt know what to do with a crooked case after it made it to the loading bench. Just throw it away. Doug

Generally, fired cases are pretty straight. If they become crooked it is in the sizing process. Having a concentricity gauge lets you look at the results of sizing, with an eye toward improving your equipment. I have learned that there are two things that work to improve how straight your sized brass is. If you are running a bushing die, the SAC bushings produce straighter brass. I have seen it. The other option, that produces outstanding results is using a one piece die that has a neck ID that gives the desired amount of neck tension without any expanding.

 

[Alex Wheeler]

Grind an angle on the end of your neck bushing.

 

[drop_point]

Generally, fired cases are pretty straight. If they become crooked it is in the sizing process. Having a concentricity gauge lets you look at the results of sizing, with an eye toward improving your equipment. I have learned that there are two things that work to improve how straight your sized brass is. If you are running a bushing die, the SAC bushings produce straighter brass. I have seen it. The other option, that produces outstanding results is using a one piece die that has a neck ID that gives the desired amount of neck tension without any expanding.

I can attest that what Boyd is saying is true.

 

[Webster]

I can attest that what Boyd is saying is true.

You can find both opinions on run out, that makes me think it's all quessing and personal opinion. There is no absolute way to test it. I don't think seeing a few better targets is a true test. Some of the best long range shooters don't measure runout. Spend the money and time if it makes you happy.

 

[drop_point]

You can find both opinions on run out, that makes me think it's all quessing and personal opinion. There is no absolute way to test it. I don't think seeing a few better targets is a true test. Some of the best long range shooters don't measure runout.

I don't believe Boyd expressed any opinion about targets.

 

[BoydAllen]

On the subject of intentionally making a round crooked, I have an H&H concentricity gauge, that is designed allow straightening of loaded rounds. Using it I bent a loaded round (for my ,262 neck 6PPC) so that it had .0035 runout. The bullet was set to engage the rifling, which is my usual practice. I chambered the round, unchambered it, and measured the runout, which was .0015. Years ago, somone who was an experienced short range group shooter told me that as long as rounds measure under .002 for runout that the differences could not be seen on the target. At the time, my usual runout was .0015 or so. None of this will make up for tune or a misread set of wind flags. IMO very small things only become important when match conditions are perfect.

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[XTR]

About 15 yrs ago i was shooting one afternoon next to an older gentleman who was a BR shooter. He told me he’d experimented with runout and he couldn’t see the difference on the tagget if it was less than .009.

I’ve personally never experienced a problem that I‘d attribute to runout. If I looked long enough I can probably find my runout tool, but once I figured out my runout was usually <.002 with no special effort it went to some dusty corner of my reloading stuff.

It gets dragged out the first time I prep brass from a new barrel.

 

[nksmfamjp]

View attachment 1618161
This tool was designed to straighten ammo, however as you can imagine, you can make stuff wonky with it also.
CW

Is this product still being produced? A quick web search looks like web site that is dead and an end dated FFL.