I've used Lee collet dies for years and have notes. One thing I have noticed is that run out is reduced, but also the variation in neck thickness was also reduced. I have had it on my mind if someone built a better, more precision version of the collet die if it might not be a viable alternative to neck turning? When I use the collet dies I turn the cases 3-4 times in the shell holder. I'm thinking the brass flows a bit under compression, thus the results. Just thinking outside the box. But the Lee collet dies do improve variation in neck thickness IMO. Thoughts?