What is runout?

[deadduck357]

I feel like if someone asks what runout is....

We should start with crook-ed

That’s meant respectfully, not smartassily

The giant scientific explanations can be a bit overwhelming

As a novice I completely agree and appreciate.

 

[6ShotsOr5?]

I feel like if someone asks what runout is....

We should start with crook-ed

That’s meant respectfully, not smartassily

The giant scientific explanations can be a bit overwhelming

That’s pretty funny and I learned a new word “smartassily”. In the keep it simple version, non-scientifically speaking, I think I learned from you gentlemen that if the case isn’t just right, it could sit a little crooked in the chamber. Also the bullet can sometimes be a bit crooked in the case, and neither one is ideal, although a little wouldn’t be a problem for most of us because other factors are usually a bigger issue, such as lack of talent for example.

 

[CTanM]

That’s pretty funny and I learned a new word “smartassily”. In the keep it simple version, non-scientifically speaking, I think I learned from you gentlemen that if the case isn’t just right, it could sit a little crooked in the chamber. Also the bullet can sometimes be a bit crooked in the case, and neither one is ideal, although a little wouldn’t be a problem for most of us because other factors are usually a bigger issue, such as lack of talent for example.

You nailed it....

Worry about excessive runout after you have found a bullet/powder combo that your gun likes.

Start with hunting a good consistent velocity, play with your seating depth, and maybe weight sort some brass if you want to develop some OCD reloading habits.

Most anything that is mass produced is a crap shoot.

You will have brands of barrels and dies that outperform others ON AVERAGE.

But there’s one in a few that are considered low quality that will outperform the supposed high quality.

So whatever you have to get you started will be enough for you to see accuracy gain or loss in your early stages of reloading.

Then invest in a few gauges and better components to make your best group not necessarily better.... but repeatable.

 

[Dusty Stevens]

http://forum.accurateshooter.com/th...ool-and-alignment-tool.3941999/#post-37208231

 

[Texas10]

You can use a caliper to measure neck wall thickness around the mouth of your cartridge (there is actually a tool made for this, a tubing micrometer if you really want to spend some money), and that will give you some idea as to how far off axis the INSIDE of the case neck is compared to the outside of the case neck. That is the starting point of "run-out".
As you seat a bullet into a case neck with a thicker wall on one side than the other, the thinner wall will stretch more, causing the bullet to shift towards that side more. This adds to overall run-out as the neck axis moves off from the case axis.

This is one reason precision hand loaders turn necks for concentricity.

As far as measuring run-out on a seated bullet, the closer to the tip of the bullet you measure, the more exaggerated the run-out will be. I don't believe I've ever read of a standard point to make the measurement.

But as others have wrote, if you're new to hand loading, run-out is towards the bottom of your list of skills you need to develop in order to produce accurate and consistent shooting ammo.

JMOP.

 

[mikecr]

This is one reason precision hand loaders turn necks for concentricity.

Necks are not turned for concentricity. Turning does not cause this.
Necks are turned for target thickness, normally with new cases, and these are less than stellar in concentricity.

Cases are typically fire-formed in a chamber (our best die) to lower runout and eccentricity.
This is normally done after turning.

 

[Dusty Stevens]

Necks are not turned for concentricity. Turning does not cause this.
Necks are turned for target thickness, normally with new cases, and these are less than stellar in concentricity.

Cases are typically fire-formed in a chamber (our best die) to lower runout and eccentricity.
This is normally done after turning.

So if you dont turn a neck and just for giggles it is .001 thicker on one side of the neck how much runout would that bullet have? We turn necks to true them up THEN get a smaller neck dia chamber to bring that clearance down. Ppc cases used to be so bad we had to turn them to around .0085 just to straighten them up so we reduced the neck size on the reamer to .262 or .263 to not have so much clearance. Now you can get away with much less so we turn them to .0115 or so to fit a .268 or .269 neck dia chamber. That cleans them up just right. So thats the reason for turning a neck- not because some douche decided he wanted a tight neck and you got stuck with extra work buying his old rifle although some may feel that way.

 

[Texas10]

Necks are not turned for concentricity. Turning does not cause this.
Necks are turned for target thickness, normally with new cases, and these are less than stellar in concentricity.

Cases are typically fire-formed in a chamber (our best die) to lower runout and eccentricity.
This is normally done after turning.

So if I switch from a paper target to a cardboard target, I should turn my necks down a bit more? Interesting!

 

[snert]

Concentricity Gauge: Accessory that creates heartburn, identifies ammunition deficiencies to the thousandth, improves groups to the bazillionth, sells Alka-selzer as a side job.

 

[rhovee]

I have done some digging into old threads of people testing run-out and shooting groups of each with no measurable difference on group size. I almost went down the rabbit hole. Mine are almost all .0003. I haven’t tested the theory myself but there are people that are way better shots than I that have. I am way more concerned with constant neck tension and shoulder bump along with sorting bullets and brass.

 

[mikecr]

There are advantages to tight neck chambers, but nothing is free.
There are advantages to tight clearances in racing engines, and most modern factory engines. But cause this without a plan and you're likely to see the opposite of advantage.

".001 thicker on one side of the neck how much runout would that bullet have?"
Your BULLETS would have far less runout(often too low to measure without a polish).

Loaded ammo TIR as measured off exposed bullet bearing (in this case) can still be well below .001, even with .001" thickness variance. Those pre-seating with mandrels see this in benefit of that action.

An advantage of a low clearance condition is less working of brass necks. This is especially useful where your annealing is less than perfect, as with tighter & tighter clearances the need of annealing for consistent tension diminishes. It can even diminish to zero need for annealing(with zero need for sizing).
Another advantage to low neck clearance is quicker neck sealing. This, reducing carbon back flow that often builds to a carbon ring interference. Combine low radial clearance with low chamber end clearance, and you'll never need to concern yourself over carbon build-up in the chamber neck.
So far these attributes help with lower ES.

Lower neck thickness reduces tension, which is reducing variance of it.
Combine turned necks with tight clearances and you will normally produce (with firing) near nothing for runout from necks. This is good, but if you then muddle up the necks(and/or the rest of the case) with a bad sizing plan, increasing TIR, the necks & seated bullets can be put in high chambered tension. This is where tight clearances are not good for everyone, and where switching to higher clearances may improves results. just don't dismiss that it was your muddling up of this that led to it. And those producing and managing straight ammo will not have this issue with tight necks.
Back to the whole straightening part. In no way does neck turning 'straighten' necks. Only fire forming can do this. And the only way those turned necks will stay straight is if you don't mess that up with your sizing plan.

Probably seems that I'm pro tight clearances
But only where I have the plan and control needed to be successful with it.
Where I've chosen this path, I've been very happy with results.
I also have no problem with normal clearances. With most guns that's what I have. There are just no tight neck advantages with these.

 

[Bart B.]

So if you dont turn a neck and just for giggles it is .001 thicker on one side of the neck how much runout would that bullet have?

It's possible the case neck axis could be perfectly parallel to the case body-shoulder axis.

But the bullet center axis will be .0005" off the axis of the rest of the case. That's the runout. Its tip will be .0005" off the bore axis. Perhaps a bit more if the case body is a thousandth or more smaller than chamber body and the extractor pushes the case head up so the pressure ring is against the top of the chamber. That tilts the bullet tip below bore center as the round pivots on its shoulder in the chamber shoulder. Typically no more than half that the case rear end is pressed up.

But this is quite repeatable from shot to shot so it's not significant.

 

[Dusty Stevens]

It's possible the case neck coukd be perfectly parallel to the case body-shoulder axis .

But the bullet center axis will be .0005" off the axis of the rest of the case. Its tip will be .0005" off the bore axis. Perhaps a bit more if the case body is a thousandth or more smaller than chamber body and the extractor pushes the case head up so the pressure ring is against the top of the chamber. That tilts the bullet tip below bore center as the round pivots on its shoulder in the chamber shoulder. Typically no more than half that the case rear end is pressed up.

But this is quite repeatable from shot to shot so it's not significant.

I know that and you know that. Like your buddy guffey says we may be the only ones though.

 

[Nature Boy]

Reloaders think necks have runout. Were do they run to? Necks do not run. They do not have legs.

fguffy-probably

 

[CTanM]

Guffey for president

 

[Bart B.]

Guffey is already a presedent. He sets new standards, doesn't he?

 

[fguffey]

I couldn’t find anything that explained what it is,

'What it is?' If it was in the die the reloader should be able to find it.

Saw a thread “GAWD DANG RUNOUT! is it my redding dies?” Don’t know what runout is but I found a lot of threads about how to fix it, and I saw case neck runout and also bullet runout mentioned so maybe there is more than one type of runout?

I have been forced to make gages/tools out of necessity. The longest was 240" long, if necessary I could have made it 240" tall but the shorter version works best when I want to know it is standing up straight or if it has a wobble.

F. Guffey

 

[KMart]

Concentricity Gauge: Accessory that creates heartburn, identifies ammunition deficiencies to the thousandth, improves groups to the bazillionth, sells Alka-selzer as a side job.

And the instructions are written by a consultant.

 

[snert]

If the tool is 240 inches long, who cares if it wobbles?

 

[CTanM]

'What it is?' If it was in the die the reloader should be able to find it.



I have been forced to make gages/tools out of necessity. The longest was 240" long, if necessary I could have made it 240" tall but the shorter version works best when I want to know it is standing up straight or if it has a wobble.

F. Guffey

Huh?