worthwhile or a waste of time practices.

[mapper]

And if the necks were uniform, and had a reduced diameter of 0.0005 to 0.001 that dadgum expander ball would not exert as much pressure inside the neck coming out of the die ( where it is not supported)

Remember, I was the guy having problems bending stems in my dies when decapping mil brass...
So I went to decapping as a separate step..

I'm aware of the stress that small diameter sizing stem gets..even lubed with a carbide ball on it

I just found this blog, and he discusses runout dimensions in relation to 600 yard groups in highpower..
http://yarchive.net/gun/ammo/bullet_runout.html

So it looks like from 0.001 to 0.003 would be good..