RCBS 56541 3-Die Carbide Taper Crimp Set .44 Auto MagRCBS pioneered and developed 3 Die Sets for straight wall rifle and pistol cases. The Carbide Sizer Die sizes the case and de primes (the carbide sizer ring eliminates the need to lubricate). The Expander Die expands the case to the proper diameter to accept the bullet, and it imparts case mouth flare bell for bullet feeding. The Seater Die seats the bullet and taper crimps.