I'm confused by your sizing procedure. I see you sizing the case down with a body die and then expanding the neck? Obviously, the neck diameter needs to be smaller, not larger, so I think there is something in your process I don't understand.
Myself, I want to size the body and the neck in the same operation. Seems to me that should be the optimal situation for maintaining concentricity.
I've gotten away from bushing dies and have moved to Forster dies that they hone to the exact neck dimension I want. These work great and don't leave that little section of the neck unsized like a bushing. It's cheap. Like $17 IIRC.
I've noticed that the lube step is a much bigger deal than I'd originally thought. If all my cases are not lubed close to exactly the same, I get varying dimensions to the shoulder. Something to keep in mind in your process.