"You are not suppose to use a neck sizing die for use in autoloaders."
Rich, the X-Die IS a full-length sizer. But, like the collet die, it uses a mandrel instead of an expander, and the mandrel pushes down on the case mouth during sizing to prevent the case from stretching. The M14 has an oversize chamber, and using a regular full-length sizer you're lucky to get three loads out of a case. Some guys claim to get a dozen loads per case with the X-Die.