I understand but new brass and new die, I wiped the interior of the die but maybe not enough.
I had the same problem. You didn't chamfer the ID & OD before sizing. Small pieces of brass brake off of the neck edge and get dragged into the die. Photos off this were posted about 1-2 years ago by someone.
If that's happening, OP can carefully inspect untouched case mouths under magnification to verify there exists "flash". A simple cure if required would be to spin case mouths a few seconds against a wad of 0000 steel wool trapped between the mouth and a cork or cardboard pad - advisable even after deburring.
Have you been able to get it out of the die yet?
Most of it, man, it is stuck like glue!! I used a dow rod and 600 grit sand paper, that didn't work so well so went to 320 just on the brass and that has worked pretty well, I think I'll put it in the tumbler and let it run overnight.
Please explain how the neck would leave brass on the walls??? Necks never touch it.
First neck through, true. But once flakes are anywhere inside the die they can and will migrate.
That particular thread concered using an expander mandrel and high seating force with new brass. Not really apples to apples, but fair enough.
I should've been more specific in our text. It's gonna take a little time for the copper cleaner to get it out if it's pretty bad. I've always had good luck with steel wool on a drill, with good copper solvent but the sell wool basically just keeps fresh brass exposed to the solvent. It usually takes at least a couple of days soaking and scrubbing periodically.
Okay, I'll try that too.
