I get sooty case necks all the time on my reloads. I don't use a whole lot of neck tension, so that may be the reason. I ignore it,, I've had it on 3 different .308 barrels, one .243, and one .223. I get wavy soot marks on factory ammo some times. I have even loaded them pretty hot 44 gr. IMR 4064 and 175 SMK over 2700 fps, anealed and all but the soot has never caused a problem and I get fantastic accuracy.