Yeah, if you must crimp, do it seperately with a Lee die. If you absolutely must with an RCBS seater die, make doubly dam sure the cases are perfectly the same length and adjust the crimping stage with extremely fine adjustments 'til you get it right. YMMV.

"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty