As a registered cheap bastard I'm still using the Rockchucker press I bought in 1973. I put Lee lock rings on my dies to let them float and self center in the presses threads. And use Redding competition shell holders to adjust the shoulder bump and still have the die make hard contact with the shell holder.
Does that lee lock ring really make a difference? Does the O ring make everything more concentric?
I’ve often looked at my Lee dies and thought that O ring looks kind of cheesy on a presision instrument, but I’ve never really given it much thought.