after many years of neck sizing only (bumping shoulders with a body die) i am now full length sizing and believe consistent accuracy is improved. with most dies there seems to be a roughness when the expander ball is pulled through the neck...even with redding's carbide button ( i spin a nylon brush in the neck). i understand this might contribute to stretching of the case neck and may require more frequent trimming. i'v tried using a wilson expander mandrel with lube and the expansion of the neck seems smoother. it is early so i can't say if accuracy is better with either. is there a consensus as to whether expander button or expander mandrel gives the best accuracy? the roughness of the expander being pulled through the neck just plain bothers me.