Neck run-out - why?

Most runout can be eliminated usually by setting up the dies properly. I leave the die slightly loose, run a case up into the die, then tighten it down into an o-ring. For the expander button, I leave it unlocked so it can somewhat stay centered with the case as it is pulled out, that is if you use a standard type FL or NK sizing die.

Another more labor intensive method is to neck turn the brass, anneal it, then it will be even thickness and hardness preventing the neck from expanding easier on one side or the other.

There are many methods of reducing runout, but first you need to determine what is causing the runout before you can correct the problem. Which is most likely why there haven't been many replies.
 
If one side of the case is thinner than the other, the thin side of the case stretches more when fired and when the brass tries to spring back the case warps pushing the neck off center.

The biggest cause of neck runout is because the expander button is locked down off center and the necks are pulled off center on the down stroke of the ram.

If you have dents and dings in the extractor groove of the case this can cause the shell holder to hold the case crooked and pull the neck off center.
 
Why? For concentricity of the round.

Here is my data (brass was Lapua in 308):
==========================
New unfired neck width: 0.334"
Once fired: 0.342"
After my Lee Collet Neck Size: 0.333" (exactly the whole way around, 0.000" runout perfect!)
After the bullet was seated: 0.035" (I seemed to have found the 0.002" tension)

Runout after Redding Die (after resizing) was:
=============================
0.333" - 0.337" (The redding seemed to have 0.004 "bumps")

Maybe my results are wrong, but I tested 6 once fired premium Lapua brass for results. The Lee had zero run out. Judge for yourself.
 
If I start with brass that has some runout, it is reduced when I size it but not gone. If I start with brass that has zero run out, I still have zero runout. That's with my redding dies, in 7 calibers.

What are your procedures for setting up your dies?
 
What are your procedures for setting up your dies?[/QUOTE said:
As mentioned above. I am sure I could be paying better attention to see better results though. Especially when adjusting the decapping rod. I am also going to have to get better at lubing the inside of the necks. I have the graphite - going to add some shot to it.
Click to expand...
 
so once you have it, is it htere for good? IE/brass is no good anymore?
Reason i ask, i sent some brass away (223) to a guy with one of those power trimmers, and he said i had some with runout. I guess i assumed it was caused by over shooting it. As why would it be on some, and not others. I resized them all at the same time. ?? I am puzzled. I will also take better care when setting up my resizing dies from now on.

I also did not lube the case necks, as i have never heard of that before. I was always told to keep lube out of the necks.
 
Neck turning has shown to reduce runout on my bench, however at the ranges I hunt and my shooting ability can't see any difference.
 
cmahussier said:
Stupid question but?
If you trim the brass will this help with the run out. Theory being to cut off the high side of the brass???
Just trying to figure this out.

Thanks
Curtis
Click to expand...

Just to clarify for ya: Trimming is to shorten, and square, the case mouth.....removing material from the end of the neck. Turning is removing material from where the neck is thicker, making the neck uniform in thickness around the circumference.
 
You are always going to have run-out. I don't think number of times a case has been reloaded determines runout. Concentricity of dies, and die set-up is most important. Case turning may help, but some BR guys say if you gotta turn the case, it is better to throw it away than to deal with whatever caused the measurable, or effective, variation in neck thickness, side to side.

BR guys want minimum runout, and use presses designed for their exacting purposes. They still don't achieve zero runout. You can seat a bullet in a case having nearly zero runout, and have signifcant overall cartridge runout because the bullet seated off center. In the end, it is cartridge run out that matters.

Guy with the power trimmer probably just wanted to sell you new brass!
 
Unless the runout is severe the average hunting rig will not show you much difference with group size. And you also need to be careful with neck turning, to much can lead to little or no neck tension on the bullet.
 
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