RCBS 3-Die Neck Set Features The RCBS 3-Die Neck Set is purpose built around the demands of the 7mm Backcountry cartridge a SAAMI-approved round that runs at significantly higher pressure than typical rifle cartridges and uses a steel alloy case in place of brass. The neck sizer die resizes only the case neck leaving the rest of the case dimensions matched to the chamber it was fired in which is standard practice for cartridges reloaded for a single rifle. An expander die follows opening the case mouth to the correct diameter and applying a slight flare so the bullet seats straight and true without shaving material on the way in. The taper crimp seater die then seats the bullet and applies a taper crimp in a single operating step streamlining the reloading process. Because this set performs neck sizing rather than full-length resizing reloaders must return cases to the same rifle they were originally fired in rather than mixing cases across multiple guns. That limitation is a direct consequence of the steel alloy case material and the pressures involved and it is addressed in the manufacturer s detailed reloading instructions included with the set. Reloaders working with 7mm Backcountry benefit from dies engineered around this cartridge s unusual specifications rather than adapted from standard rifle die designs. The RCBS 3-Die Neck Set for 7mm Backcountry is available for sale at GrabAGun for handloaders running this cartridge. RCBS 3-Die Neck Set Specifications Manufacturer: RCBS Caliber: 7MM Backcountry In Set: 3 Die Type: Neck Sizer Expander Taper Crimp Seater Available At: GrabAGun