Oh, I'll continue, just not so rabidly.
I've measured a lot after reloading and before firing and as far as I can tell, they're square as possible.
Ponder this.
The chamber isn't real tight against the case walls when seated. Given the mouths don't touch the lip to keep them square. Given they're being held back one one side by the extractor claw and pushed forward on the other side by the ejector plunger. Perhaps they're canted in the chamber ever so slightly and one side grabs the walls a little tighter upon ignition. Perhaps the extractor distorts the rim beneath it slightly stretching it so the case appears longer on that side, but that would not explain the asymmetrical sooting. I should mark the claw side with a sharpie dot when I hand feed them ( 500 shots so far all hand fed)
I know that when I see sooting, it's mainly down one side and I know from reading on these forums that other members experience that as well. As for length variation, it runs about .001-.0025 from one side to the other. More pronounced with lighter loads. I just trim them after resizing so the high side is brought down to the low side. It's NBD, just another enigma. It's 08:30 and I'm off to the range. Have a fun Saturday everyone.
Hoot