Originally Posted by Delta Hunter
You may be sizing your brass with perfect concentricity on the outside of the neck, but with that die the difference in neck thickness will be tranferred to the inside of the neck and therefore the inside surface of the neck will not be concentric to the axis.
Thanks for the replies.
That's partly my take on it too. Just to be clear, I'm not doubting the Wilson tool at all.
I'll run a K&M mandrel in a few necks over the weekend (don't have a die in 300WM with an expander) and see how that changes things. However, the relatively consistent neck thickness makes me wonder if that's the "full story".
I'm not wanting to get ahead of myself with a thread for later once I have a runout gauge, but I suspect that the necks are a bit shaped like this () on fired brass. I'm not sure why - maybe the chamber has too much clearance for the thinnish Winnie brass (have no idea if that will do it), but the runout gauge will tell me if that's so. That may increase runout and lead to peculiar results when run into a neck only sizer.