First time sizing this new 6BR Lapua brass. Using 375 Whisper Hornady dies. Lubed and first ran through .310" Hornady expander with no problem. After lubing again and running over .375" expander, I see this mark. When I run my fingernail over it, there's a noticeable jump in diameter for the neck brass closer to the shoulder. (Seems like something more akin to a false shoulder than a donut.) Mic'd neck on side of that mark closer to the mouth at about .3891"; on the side closer to shoulder is about .0060" higher (.3950").
Inside the neck, it looks as if the "unsized" portion (closer to the shoulder) is a smaller ID that the "sized" portion of the neck (closer to the mouth).
It's like the neck is not being sized all the way down. Baffled. Have compared die body to case gauge I bought from SSK--all seems fine. Also highly doubt that the specs in the Hornady sizing die body is off.
Cases chamber. Feels like I'm missing something basic. Advice? Given that they chamber and I'm using exclusively for subsonic rounds, should I fireform and quit worrying about it?
Inside the neck, it looks as if the "unsized" portion (closer to the shoulder) is a smaller ID that the "sized" portion of the neck (closer to the mouth).
It's like the neck is not being sized all the way down. Baffled. Have compared die body to case gauge I bought from SSK--all seems fine. Also highly doubt that the specs in the Hornady sizing die body is off.
Cases chamber. Feels like I'm missing something basic. Advice? Given that they chamber and I'm using exclusively for subsonic rounds, should I fireform and quit worrying about it?
