I form all kinds of cases from 308 Win and 30/06, headstamp means nothing. Also made 6.5x47 Lapua from Rem 22/250, shoots 1/2" at 200 yards in a deer rifle. Made 6 XC from 308 Chinese military brass, PMC 308, and Lake City Match 308, ended up with .400 long necks. I ordered a .275 Piloted neck reamer from PTG, and the gunsmith cut the neck longer in the chamber, then throated it for the 105s. Accuracy with even the Chinese military brass is nothing short of incredible.
In my life, I had one mix-up at the range. I was working up loads for a 7 Rem mag and a new 7 STW. I shot a 7 Rem mag in the 7 STW, and ended up with a case neck about 1/4" long, but no problems at all fire forming that case! I never did that again!