Trim a bottleneck case once—and never trim again This sizer features a specially designed mandrel with an expander ball and decapping pin attached. The patented design eliminates the need for repeated trimming after an initial trim of .020 inch off the maximum length to standardize the case. The X Die doesn’t shorten the length of the case: The mandrel reduces the growth caused by the case mouth contacting the mandrel during sizing. Because of an extremely close tolerance between the mandrel and die neck wall, the neck wall of the case does not thicken as the case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few thousandths of an inch, and then stabilize below the maximum case length with no discernable loss of accuracy or case life.