Case neck runout when full length sizing

[NoahbodyImportant]

Redding Full Length Sizing Die with free-floating carbide button
Forster Co-Ax press

Fired cases have very little runout

After full length sizing (using Imperial Wax) runout is now much greater!?! WHY?

Should I try another full length sizing die?
Should I remove the free-floating carbide button?

Any suggestions greatly appreciated.

 

[Immike]

Can be alot of things. Are you annealing before sizing? The thick side pulls on the thin side. I have rotated my shell holder and changed my run out. Everything has a flaw. Look at everything.

 

[ridgeway]

Remove your expander ball and see if you still get them same run out.

 

[NoahbodyImportant]

Removing the new free floating carbide button, no new runout.

I just purchased the free floating carbide button because the expander button that came with the FL die was causing runout.

Conclusion, not using the expander button results in no new runout.

 

[ridgeway]

Maybe its the die? In numbers, how much runout are you getting on a fired and then sized case? Do you have another die to try?

 

[Phil3]

See some of my recent posts. Been exactly where you are. I have the Co-Ax press, the Redding FL die, and carbide floating button, and had the same problem with 223 Remington Winchester brass. I suspect the runout is because the expander button pulls so hard on the neck, that it stretches it and cocks it. The neck is most likely cocked because one side of the case and neck is thinner than the other. That side stretches and gives before the other side. A .002" variance is around 17% difference in thickness and is enough for one side to move before the other.

To combat this, I used the Redding carbide button. No real change. I ordered a Forster FL die, and amazingly, that seems to create less runout. And it also feels like it takes less effort to move the expander through the neck than the Redding. More testing is needed for any real conclusions. Also, I used a Lee Collet die and a Redding body die, and this seemed to work well. This avoid use of the expander all together.

One solution? Better brass.

Phil

 

[amlevin]

Also, I used a Lee Collet die and a Redding body die, and this seemed to work well. This avoid use of the expander all together.

One solution? Better brass.

Phil

+++ on all three.

Lee Collet, Redding Body, Better Brass.

 

[savageshooter86]

Can you achieve different neck tension by slowly turning die in more or less? Seen you can do this with regular press, but not sure about this one

 

[Phil3]

If you mean screwing the die further into the press, then that should have no effect on neck tension in any press. For a FL die, screwing the die further into the press will set the shoulder back a greater distance. But, the neck size (and resultant tension) is always set by the expander button. A bushing die will set the neck tension by selection of bushing. A Lee Collet die will set neck tension by diameter of mandrel contained within the die. A body die doesn't touch the neck at all, no matter where it is positioned in the press.

On a conventional press, the die is threaded into the press and locked down with a locknut. On the Forster press, the locknut is secured to the die, and the die/locknut assembly is slid into a slot that fits the locknut. Adjustment up and down is achieved by screwing the die within the locknut. The design permits instant changing of dies by sliding one die/locknut out and sliding in another die/locknut. There is a spring loaded button so the die/locknut snaps in and out.

Phil

 

[savageshooter86]

I know all the above. A few people have told me they don't turn the die in all the way and therefore the case neck isn't completely forced onto mandrel of Collet die. They say this gives them slightly less neck tension than roving the mandrel fully. I know at the point you touch mandrel, the case neck can't be sized any smaller and additional turning in of die may damage it.

 

[BoydAllen]

(to the thread starter) Your die needs to be lapped out so that the expander has less "work" (dimensional change of case necks) to do. Pull the expander assembly and size a case. Measure the neck diameter and compare it to one that was sized with the expander in place. This should tell you the source of your problem. The difference in these diameters is too great, and in process of being expanded up, the axial pull on the case is large enough to exceed the yield strength of the case at the shoulder, causing it to yield asymmetrically, cocking the neck relative to the case body. The answer is to have the die neck honed out so that the expander only does a couple of thousandths of work, at the most. This amount of expanding will not cause problems with case straightness. When a friend had a custom die made by Hornady, for one of his varmint rifles that he takes a clean up cut on with his neck turner, it was ordered so that without the expander, he has .003 neck tension, and with .002 either option gives straight cases. Another option is to use a bushing FL die. With these, for unturned necks, you can choose a bushing that lets the expander do a little work, and the IDs of sized case necks, and bullet seating force will be more consistent. If you turn, you can eliminate the expander if you like.