SINCLAIR INTERNATIONAL GENERATION II LARGE CALIBER EXPANDER DIES Large caliber die body for use with our large caliber mandrels. Expander dies are an essential companion to neck turning tools. They enable the expander mandrel to produce the correct fir of the case neck on the neck-turning mandrel which is vital for accurate, easy neck turning. Expander dies and mandrels can also "iron out" dinged case necks, set consistent case neck size for uniform bullet tension or to "neck up" cases one caliber at time for wildcat cartridges. Our Generation II Expander Dies completely capture the mandrel within the die so the mandrel Mfg: Sinclair International