[amamnn]

I would have posted pretty much the same thing as Nick did, with one difference:

I've had the opportunity, or misfortune if you prefer, of testing a Lee, a Redding and a Forster FL sizing die on the same cartridge--yes I ended up buying all 3. I had a lot of trouble getting necks to remain concentric with the 6mm WSSM. Eventually, using the Forster, which has a different design as relates to the position of the expander ball, I was able to size cases to my satisfaction. I should have known better, since I use and have used Forster custom FL dies for 6ppc and 6 BR. My only excuse was that the time, dies for the WSSMs were scarce.

Just another observation: The finest seating die on the face of the earth will not align a bullet in an off center neck any better than the cheapest one.