Reloading various calibers it came to my attention that in 308 cartridges crimping the necks is recommended. Does crimping cause higher pressures ? as the projectile seems to have to overcome the neck wall resistance in microsecond time before starting travel up the barrel. All my rifles have not had any problems without having shot reloads not crimped. The only crimped loads were factory loads and I see no advantage to the crimping , am I missing an important step ? Also I have experienced full sizing with small base dies having 6 out of 20 casings not chambering prior to priming & charging. I removed the decapping pin & ran them thru a neck resizer 2 or 3 cycles with success in chambering the cases. Is this a common problem while reloading ? I always dedicate brands of casings to different rifles of the same caliber to prevent chambering issues ( 30/06 = Sako Federal cartridge , Weatherby = Win/ west) etc.