Neck Runout Troubleshooting Help Needed

[JDSwim3]

Redding competition neck sizing die inducing 3-4 thou runout, as measured on 21st Century concentricity gauge. Die being used in hard mounted Rock Chucker Supreme.

I've tried the following, all with similar results:
- Fully tightening the die
- Allowing some free float in the die
- Free floating the die with a rubber o-ring
- Fully tightening the die with a rubber o-ring

Other potential causes as I see it, and although inexpensive, hoping to fix without additional purchases:
- RCBS case holder manufacturing flaw (misalignment with die)
- Die bushing manufacturing flaw or out-of-square internal interface with die

Don't have the equipment to check, but I guess there's a possibility the press ram is misaligned with the die body.

Any help with troubleshooting steps is greatly appreciated!

 

[358WCF]

Is there a decapping/expander stem on your sizing die? If so try removing it.

Have you tried removing the spring clip for the shellholder? I've read that an O ring can be used to somewhat keep the holder in place but allow it to float. No problems with my Co-ax.

 

[Idaho-Lefty]

WHEN,.. all else, Fails,.. treat yourself to, some Forster Dies !
Thank me, later !

 

[skeeljc]

3-4 thou runout sounds about right for a neck sizing die. My Redding FL dies produce less than 0.0005" runout without an expander. The problem with a neck die is the case body is just rattling around in the die.

 

[varget204]

Had the Same Problem,Sent it back to Redding,Got it back, case were still .002- off, Got with a Letter Explaining .002 was With/in their Tolerances, NEVER Bought another Redding Die, for 150-175 dollars should be a lot better

 

[K22]

Just curious - do you have a "run out" problem?

In other words, have you narrowed down run out as a problem on target?

 

[JimSC]

Are you backing off on the bushing retainer about 1/4 turn to allow the bushing some float ? I use the Redding full length S sizers with non coated Redding bushings and 90% of my cases come out with less than .001 and never more than .0015 runout.

 

[Mikemontminy]

Put the dial indicator directly on the rollers of your 21st Century gauge to see if the rollers are turning true. I have two rollers on my gauge that are out .002 giving me false readings.

 

[ronemus]

How much are you necking down your brass? It's a known problem with bushing dies that if you size more than 0.003-4" at once you'll get runout. Unless you have a close-fit custom chamber, that means sizing in multiple steps to reach the desired size.

How are you supporting the case and where are you measuring runout? That's not a trick question - there are many measurements that fall under the category of runout, and they're not the same by any means.

Have you neck turned your brass? If not and you're measuring runout on the bullet, you will need to turn - it's the only way to make the ID and OD of the neck colinear. The chamber and sizing die can only control runout of the exterior of the case, and unless you've neck turned the bullet will still have runout.

 

[Keefe300]

I have run into this issue before. My problem was the die bushing. I have found this to be my issue on 4 different occasions. My setup is the same as you described, RCBS press and Redding Comp neck die. You can also talk to the bushing maker, they will usually ask you to send them in so they can check them.

 

[STS]

I probably have 30 to 40 bushings in a box that I have used at various times in addition to the bushings that are in my dies. In a second box I have 5 bushings that have a hole that is either out radially or not concentric with the centerline of the bushing. You need a tubing mic to measure various places around the bushing on each end to figure out if the bushing is usable or not. Some are not usable.

 

[Uncle Ed]

The directions with a bushing die tells you you should hear the bushing rattle. The bushing floats and can move from side to side and even tilt when reducing the neck diameter. Bushing dies work best with tight neck chambers where the case neck diameter does not need to be overly reduced in diameter. And in a standard SAAMI chamber the neck needs to be reduced in steps to help reduce neck runout.

Tech Line & Tips (FAQs)​

https://www.redding-reloading.com/tech-line-a-tips-faqs​

Concentricity & Bushing Dies​

From tests we have conducted, we have learned that selecting the correct bushing is the most important factor in producing sized case necks that have good concentricity with the case body. Our tests showed that case neck concentricity is directly proportional to bushing size. In other words, as you size case necks with progressively smaller bushings, the concentricity gets progressively worse.

We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

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And as stated above you would be better off with a Forster non-bushing full length die that would give you less neck runout. And if you think the Forster die is reducing the neck diameter too much you can have the neck of the die honed larger.

Weekly Gear Update - 036 Forster Honed Dies​

 

[Dusty Stevens]

The FL version of your die is a great die. A neck die doesnt have body support and a neck thats thicker on one side will cause this issue with the included expander

 

[EEP]

I had the same issue with a Wilson die. Sent it back and they replaced it. They requested a couple fired cases along with the return. The one they sent back to me has no runout.
My recommendation is to call their tech service and explain what you’re seeing. Most likely they’ll do the same as Wilson.

 

[D-4297]

I know it's blasphemy to suggest it , but I will anyway . Are you de-burring the outside of the necks on your cases before running them through the die . If not , even the smallest of burr will have a drastic effect on run-out . Sometimes we all get in a rush to get rounds loaded before a practice day , or match , and we overlook that step . "That tiny little edge burr won't matter THAT much" . Yeah ,.......Right .

 

[skeeljc]

The directions with a bushing die tells you you should hear the bushing rattle. The bushing floats and can move from side to side and even tilt when reducing the neck diameter. Bushing dies work best with tight neck chambers where the case neck diameter does not need to be overly reduced in diameter. And in a standard SAAMI chamber the neck needs to be reduced in steps to help reduce neck runout.

Tech Line & Tips (FAQs)​

https://www.redding-reloading.com/tech-line-a-tips-faqs​

Concentricity & Bushing Dies​

From tests we have conducted, we have learned that selecting the correct bushing is the most important factor in producing sized case necks that have good concentricity with the case body. Our tests showed that case neck concentricity is directly proportional to bushing size. In other words, as you size case necks with progressively smaller bushings, the concentricity gets progressively worse.

We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

------------------------------------------------------------------------------------------------------------------

And as stated above you would be better off with a Forster non-bushing full length die that would give you less neck runout. And if you think the Forster die is reducing the neck diameter too much you can have the neck of the die honed larger.

Weekly Gear Update - 036 Forster Honed Dies​

I am in the process of transitioning from a Redding FL type S bushing die to a honed Forster FL die for my .223 Remington. Right now there are no .223 Forster FL BR dies to hone. I do have a Redding FL die. The Redding die convinced me that fixed FL sizing gave the lowest runout. My Redding FL die sizes the neck to 0.239" in diameter. The runout without an expander is less than 0.0005" t.i.r. I do not need to size the neck down to 0.239". I have ordered a Forster FL BR die to be honed to 0.245" dia. I can expand the neck in a separate operation with a 0.223" dia. pin to get the neck tension I want and only increase the runout to 0.001" t.i.r.

 

[PopCharlie]

Make sure you take the thread slop out before you tighten down your die..

PopCharlie

 

[MattPeetz]

People worry about some of the most senseless stuff

 

[paulT]

Body die to bump necks 1-2 thou and size body along with Lee Collet neck size die will produce very concentric brass with very little runout.

 

[skeeljc]

Seems to me that anything other than a one piece FL sizing die increases the potential for runout. Runout is usually measured as the concentricity of the case neck to the case body. If you size the case body separately from the neck you can induce runout. Bushing dies allow the bushing to float which can cause runout.

The real question is how much runout does it take to affect accuracy? I can size .223 with a bushing die and a second operation expander and have .003" t.i.r. runout (neck vs body). I can size the same cases with a FL die and second operation expander and have only .001 t.i.r. runout (neck vs body).