What you're seeing is probably not an actual donut or at least not one to be worried about. Redding bushing dies are made in such a way that they won't size the entire neck. There's always just a little bit that's not sized....that's what you're seeing.
Load 'em up and shoot 'em. After firing, see if a bullet will freely drop into the case through the neck. If it does, you're good to go. You can also use the old bent paper clip to check the neck/shoulder junction.
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