Mike, you are correct about the color change. I would call it a very slight "antiquing". I only see it on a polished case.
I do have a question for you though: are you using an IR thermometer to get the temp of the lead? For whatever reason mine does not like molten lead, but read just fine with the empty pot. I tested it against other thermometers and it worked just fine, but I CANNOT get it to read the molten lead reliably. So I have to go with a regular pot thermometer.
I was seating some bullets in the dipped cases, and had some that were way too loose still. All cases measured .304 ID for a .308 bullet, so I should have had some serious grip. Neck wall thickness was ~.012 - .013 (this was junk Winny brass). What gives? Not dipped long enough?
If I read you correctly, the answer MAY be to drop the temp some (so the oil doesn't smoke off as fast) and hold it in there longer OR get an oil that lasts longer at the current temp. Any other ideas to resolve this issue?
Oh you could overheat a case,, you could screw it up,, you could get hurt..you can not over heat a case to failure