I know this isn't directly addressing your runout issue, but...

I have 15 sets of RCBS Dies, 4 sets of Forster Benchrest dies, 2 sets of standard Redding dies, 2 sets of Redding competition dies, along with 2 Redding bushing dies (in PPC and BR), 4 sets of Lyman dies manufactured in the late 50's/early 60's and a set of Wilson dies in PPC. After reading threads on other forums about the tolerances of the newer dies, and listening to some pretty knowledgable guys who convinced me to (One) measure the expander ball on my dies and (2) buy and/or find some Lee dies to measure.

I have dies from RCBS, Redding, Forster, Lyman, and now Lee in 270Win so I chose those dies to compare/measure (My "competition" guns are about playing--it's my huntin' rifles I'm serious about anyway) I also have a runout setup that I was able to measure the runout of the expander balls, and I measured the difference between a case sized without the expander verses a loaded round in the same manner as Bob338 described.

To make it short, the expanders on my old Lyman dies, my 1970's RCBS dies (2 sets), my 1980's Forster die, and a brand new set of Lee dies and a borrowed set of 3 year old Lee dies all were well within specs (also within .002 of one another) and showed runout less than .002 (I hope my technique was accurate with my runout gauge).

But it was the newer RCBS and Redding dies that showed at the "edge" or outside of tolerences (or at least acceptable tolerances for me). Runout was horrible on the newer RCBS's and Reddings including a RCBS necksizing die (no wonder I was getting crappy runout).

The best? My 1972 RCBS FL die, the Forster die, and both sets of Lee dies!--go figure. I think this may be a good case of where I am as much duped by Madison Avenue advertising, price (more expensive is better), and "common wisdom".

Casey

Bigcountry--It's possible with the undersized ball there is just so much tension when seating that the bullet is going crooked when seating. Maybe when you get that new ball it will all work itself out. It's funny though when you read that some of these guys have been taking the entire ball and stem out of the die and somehow they are saying the bullet seats just fine. (I never could figure that idea out!)

Regarding runnout with ANY brand die many many times when you get a die, the sizing stem is not seated in the center of the die from the manufacturer. I have found that by making small turns of the seating stem you will eventually find a sweet spot where it winds up very close to being in the center of the die. If you are not getting good runnout at the case mouth after sizing make a 1/32 turn up or down of the sizing stem---size some more---if not good make another 1/32 turn--size some more. I guarantee that eventually all of a sudden you'll start getting good runnout. I have had exceptionally good results with cheap hornady and high quality forester.

I have been fighting runout issues. And have tried all the regular avenues to find the offending reloading component. someone asked me if I get shavings alot unless I deburr or chamfer the inside mouth. I said yes, I do. So I measured my expander ball of my 300RUM FL RCBS sizer. It measured .3058". Called RCBS and they said spec is .3065 to .307" and it looks like it isn't opening the mouth up enough and the rough bullet seating could be causing my issues. What do ya think? They are sending me a new one. In the mean time, I am going to use another one from my .308Win.

Also--regarding chasing runnout and hunting ammo. If I'm going on a high quality hunt where shooting might be long distance I segregate ammo. I put a "green" dot with a sharpies marker on ammo that turned out .002 and less. I leave the ammo that turned out .003-.005 with a plain primer and anything over .005" gets a black primer. I've never had to get into my "PLAIN" ammo. But when the hunt is over and you find something you might want to plink at use the black ammo---I'll bet you'll find it goe's right where it should too!!! And you'll get all kinds of confidence when you slide those "green" shells into your gun---kinda like there's now way you can miss!!

Totally agree with what RCBS is telling you.

Size a case without the expander. Measure that and subtract from the neck of a seated case. That number should be no more than about .010"-.011" difference. If it's more than that RCBS may also need to polish out the neck. I'm surprised that wasn't mentioned.

There shouldn't be any difference in the expander ball in your two dies. They are mostly all .001" smaller than the caliber which should leave a "grip" of about .002" or slightly more. Any more than that is overkill. Good temporary solution you found.