OK, here’s what is probably happening. First off, this here is Kentucky brass. This is not some namby pamby brass. It is strong in the shoulder. When I push the .262 mandrel through, the neck expands and stays at .262. The shoulder neck junction, which is stout and strong like Kentucky brass oughtta be, expands but then springs back as the mandrel retreats, leaving a burnished ring. The retreating mandrel leaves the balance of the neck at .262 making it look like a constricting donut has been built into this fine Kentucky brass. But no, it was created by the mandrel and the thicker brass inherent in this part of the case. Now the neck gages at .262, the neck/shoulder gages at .2605 - .261. This constriction, while not substantial, is abrupt enough to allow me to f*ck up some fine brass while seating the Berger 156 EOL boat tail below the shoulder. The solution for me is to hit it with a larger mandrel or a larger expander ball. I do regret not checking ID and case weight right out of the box to see if the two boxes I have were substantially different or not. On the brighter side, I now have pin gages .260 through .265 in .0005 increments which will be put to good use.
Anyhow, that’s my conclusion after digesting much of your fine advice, and checking with pin gages.
918V, you were right, it’s not a donut. Steel head, you were right, ADG brass can be stout.
I did send an email to ADG with pics and a detailed summary, asking for their thoughts, and will let you know what they have to say.
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