The RCBS X Die Small Base Die Set for .223 Rem/5.56 NATO is a reloading die set engineered to reduce the need for repeated case trimming after an initial standardization trim. Its mandrel-mounted expander ball and decapping pin are integrated into the X Die sizer to control case neck growth during repeated sizing. The set pairs the X Die Small Base Sizer with a standard seater die for a complete starting setup for those new to reloading this caliber.
Key Specifications
- Designed for the cartridge .223 REM/5.56 NATO.
- Die style is Small Base Dies to work with small-base reloading equipment.
- Includes an X Die Small Base Sizer and Standard Seater Die as a set.
- The mandrel features an expander ball and decapping pin attached to the sizer.
- The design recommends an initial trim of .020 inch off maximum length to standardize cases.
- The mandrel reduces growth caused by the case mouth contacting the mandrel during sizing through an extremely close tolerance between the mandrel and die neck wall.
- Cases sized repeatedly in the X Die will initially grow a few thousandths of an inch and then stabilize below maximum case length with no discernable loss of accuracy or case life per manufacturer notes.
The RCBS X Die Small Base Die Set offers a practical, engineering-driven approach to minimizing trimming during repeated sizing cycles. Its integrated mandrel and patented features make it a straightforward choice for reloaders seeking to standardize .223 Rem/5.56 NATO cases while preserving case life and consistency for range use or target practice.
This description was generated with AI and may contain errors. Verify specifications and legal restrictions with the manufacturer before purchase. Provided “as-is” without warranties or guarantees.




