RCBS Full-Length Die Sets are precision-machined from our proprietary die steel to exacting tolerances, then undergo a meticulous finishing process to deliver the highest quality dies for hand-loaders. Each set includes a Full-Length Sizing Die and Bullet Seating Die, designed specifically for reloading bottleneck cases. The Full-Length Sizer Die features an Expander-Decapping Unit and is engineered to bring cases to SAAMI minimum cartridge dimensions. It sizes the outside of the case, de-primes and expands the neck to accept the bullet, while vents in the die help prevent case damage caused by trapped air and excessive lubricant. The headspace is held to minimal tolerances to avoid altering the case body length during sizing. The Seater Die includes a built-in roll crimper that secures the bullet as it's seated, ensuring a consistent and secure crimp for reliable performance.