Just loaded some 130gr plated 9mm bullets originally designed for 38 Super: used the flat seating stem from the Hornady dies and it put a nice little flat point (about an 8th of an inch in diameter) on the nose. This actually would lead to a little longer (than measured) effective OAL...?

In the past I have certainly noticed rings on plated bullets when using the other (RN/HP?) seating stems, most often on 9mm. I think it has more to do with the thickness of the plating. Hardly ever on the Berrys HBFN-TP or HBRN-HP versions.

Cheers!