I've had only one problem using RCBS X dies on military brass, and that was my fault. I had to replace the deprime stem and didn't check the neck expander size. Wound up with over 700 pieces with a neck size of .218, that couldn't be trimed. They were consistant, just too small.
Un-necessarily having to resize 700+ pieces is no small trick, but it taught me a valuable lesson about assuming that what I ask for, was what RCBS actually sent me. We both goofed, but I had to pay the price.