I think I would get better results to making 8mm by using a hand reamer when cutting down and reforming 30-06 military brass.
I don't have any issues with chambering after reforming but I think the neck is thicker and swaging down the lead bullet a bit. I looked at 8mm reamers and they would still seem a bit tight to me at .31 for a .324 lead bullet with PC.
If I first size outside of case only (Lyman 8mm cut off die) ream to .31 with an 8mm ream, then run through a sizing & depriming die should I expect the neck size to be improved by removing excess metal before sizing inside and outside of neck? I think the Lyman cut-off 8mm die should size outside causing any surplus wall thickness to be pushed in where it can be reamed. Then second run with regular sizing die that does inside and outside of neck will give me a proper sized neck.
Just want to make sure I order an appropriate ream and apply it at the correct stage of the process. I use 30-06 military brass without a caliber stamped on the head that would be inappropriate to the completed conversion to 8mm. Don't have anything to use to remove stamping on the head so I make it so the head isn't a "false" caliber label. The few I made so far "work" but I see some loss of accuracy with them, I suspected swaging the bullet down under what an old milsupr Mauser bore needs.