In messing with this problem I've come to think the problem is not the thickness of the brass but my top punch deforming my boolits during re-sizing in the sizer luber press. As I examine the points of the boolits, it appears some are more pointed and some are flatter, all from the same mould. The boolits are being deformed in the re-sizer. The 525 gr boolit with a blunt nose rests right up against the rifling when chambered.
I took a couple cartridges that did not chamber and hand forced them to see where the marks would be, yup rifling marks on the lead of the boolit. So deforming the meplat of a blunt nose 525 gr boolit that is already at a critical C.O.L. is what I think is preventing the cartridges from chambering. And now I have loaded W-W brass that also does not chamber.
I have a Lyman Sizer-Luber (two of them actually). A Star sizer luber would prevent this problem from occurring. The first step is to send my unsized and sized boolits along with the H&I die to Lyman. I think I need a new H&I die.
My Lyman mould has a BV after the 457125. I don't know what the BV stands for and if this could relate to the deformation from the H&I die.