I have FL dies by rcbs and redding for my 22-250 and both cause no case neck run out. If the case has .0015 run out before sizing, that is what I get after, or better. After reading that best accuracy will be achieved with neck sizing only, I bought a rcbs neck die. It leaves cases with .005 run out or more. I then bought a forster neck die, and get .005 run out or more. I've tried them with and without the expander and get the same thing. I've adjusted and readjusted the dies with no luck. Is this common with neck sizing dies? If I FL size with out setting the shoulder back, is this just as good as neck sizing only?

I have the hornady 30 cal neck sizer. It drives me crazy--I will use it on new brass and get about .002" runnout pretty consistant. Then I take a fired shell (which is now perfectly concentric) and I get anywhere from .002-.006". Sometimes I think the expander ball catches the burr left from a factory crimp. Maybe my shellholders are too sloppy or I'm not being consistant at putting the shell into the shellholder--BUT IT DRIVES ME CRAZY TOO. At least you know you're not alone--maybe we'll both get the answer here!!

JCCD & Don __

Let's toss a "could be" in here. Your relative perfection after full-length resizing indicates that the diameters of the die are quite concentric. Any variations "could be" due to differences in "spring-back" by reason of differences in wall thickness.

In neck-sizing only, the body of the case is merely "brushing" the sides of the die, all of the work being done at the neck, thus allowing the body to move with some freedom within the die. Unless the centerlines of the neck and body are well-aligned to begin with, they will be mis-aligned after neck-sizing, resulting in variations in out-of-concentricity beteween body and neck.

This would indicate that the as-fired case was out-of-concentricity prior to neck-sizing. A matter of making a cast of the chamber and checking it on whatever device you're using.

Please excuse the excessive "blat".

Good shooting.

Robert

NOPE--I appreciate the try but, the brass is concentric before sizing in my case. There is something just plain "wierd" going on that's pulling the case neck off to one side or something. As I think about what you said one thing does "pop into mind". The only place that shell is being held is at the two furthest points--the case mouth and the shell holder. In regular sizing the grip up and down of the case may help center it more perfectly. Being that the leverage points are so far apart during neck sizing it wouldn't take much to "pull the shell" off center a few thousanths of an inch??

Could be your shell holder! This will drive you crazy but when I first started shooting 1,000 yard competition I was using Lee SDB dies (like $11 a set) and was getting no runout (that I could measure with a NECO tool) with my GI .308 brass. My Forester benchrest dies are also nearly as good. All in my RCBS Rockchucker too.
Try a different shell holder...

The expander ball/decapping rod may be your culprit. If the rod is bent, even slightly tweaked, it will throw your case necks off. Pull the decapping assemblies out of your dies and resize a few cases. Measure the before and after runout to see if this is the problem. In fact you probably could measure the runout of the decapping rod as well.

I know about fiddling with the expander stem.
I know just what you're saying in how a slight turn can make a big difference, but in my case about 60% of the ammo is turning out pretty good and about 40% bad. If the stem was out of alignment I wouldn't get the good 60% worth. I think the shellholder has merit---possibly!!!

I guess my problem could be neck wall thickness variations and the fact that the case walls aren't supported during the sizing. I haven't turned the necks. It isn't the expander/decaping rod, because i've tried them with these removed from the die. Thanks for the suggestions. I think I will just use the FL die for now.

Just for an experiment, try removing both expander balls from your Hornady neck sizing die and your FL RCBS die. Size a couple of cases in each and measure the neck diameters. I'm wondering if your neck die sizes them initially smaller than your FL die.

I've heard that the more brass is worked, the greater the impact to concentricity, and that's one reason why Lee's Collet die and Redding's Bushing dies (when fitted with a proper bushing) have such a good reputation.

Martindog

The average neck die especially when used in conjunction with a standard dimensioned chamber will frequently, in fact, usually produce brass with an eccentric neck. This because the brass is usually thicker on one side and or harder on one side. Also the body of the die does not support the case. It is seldom the fault of the rifle.
Most times fl sized brass will produce better accuracy simply because it produces straighter ammunition.
With BR rifles where sizing is minimal and dies are closely matched to the rifle chamber this does not apply.
Mostly I have no use for neck dies except for the custom dies I make up for my BR rifles. Regards, Bill.

JCCD, Using both rcbs dies, fl and neck, the fl die gives me the best accuracy.But better yet is Redding fl bushing die without the expander, used with neck turning.243winxb