The RCBS 7mm Backcountry Die Set is engineered specifically for reloading the 7mm Backcountry cartridge and its steel alloy case. Because this SAAMI-approved cartridge operates at pressures significantly higher than conventional rifle cartridges and uses a steel alloy case rather than brass, the reloading process differs from traditional brass-case reloading in several important ways. Full 7mm BC reloading instructions below. The three-die set includes: Neck Sizer Die: sizes the case neck only Expander Die: expands the case mouth to proper diameter and applies a slight flare (bell) so the bullet can be seated Taper Crimp Seater Die: seats the bullet and applies a taper crimp in one operation Because this set neck sizes only, cases must be reloaded for the same rifle they were fired in.