I did exactly what you want to do. Use Lapua brass in my 25-06.
The steps I took were:
- size in a FL 30-06 die with the expander removed
- size in a FL 280 die, didn't bump the shoulder, no need to
- size in a FL 270 die
- size in a FL 25-06 die
Expanded the case neck for neck turning
Turned the case necks
I played with using bushings, but I didn't have them in the correct diameters. The opening in the bushing doesn't have much of a radius, so you are limited how much oversize a diameter it will accept. My experience is the smaller steps you take the move consistent the neck thickness remains. YMMV
The first 50 I did I neck turned them as 30-06 brass. The neck shoulder junction now is part of the shoulder and it looks unusual. So the second 50 I turned the neck after I completed sizing them down.
Here is what they looked like. None were lost and no shoulder wrinkles.
View attachment 1296414