Re: What's the full-length sizer doing to my new brass
BP,
Your case mouth has tiny particles that are coming off, and it is galling your brass, and your die.
First, take your die apart and clean it with a stout solvent, get the brass out of it. Then lube it,neck especialy.
Then if your case mouths aren't dinged up too bad, chamfer and deburr them, this will cure it, of coarse with lube. If they are dinged, just run up through expander, then chamfer.
Your lucky it is Lapua brass, it is clean, other brands would have galled your whole die, espeially from expander pulling loose shit from inside the case.
Lube every 5th case mouth with Imperial. Also, set the die back to where you started, do the whole neck.
Hope this helps, if not pm me.
Most people would have just shot this before prep, what I would recommend to do.