The RCBS .223 Remington X-Die Full Length 2-Die Set (Model 37212) is a specialized mechanical reloading tool designed to resize bottleneck rifle brass and seat bullets while completely eliminating the need for repeated case trimming. Engineered for the .223 Remington and 5.56×45mm NATO calibres, this set features a standard 7/8"-14 thread, ensuring wide compatibility with standard single-stage and progressive reloading presses. Because it is a fully mechanical hand tool, it requires no electrical power or Australian compliance certifications, making it directly compatible with any standard manual reloading bench.

The core of this set is the patented X-Die sizing system. In standard full-length sizing dies, bottleneck cases stretch and grow in length during resizing, requiring frequent trimming. The X-Die mandrel system resolves this by regulating brass flow. After an initial trim to a precise baseline of 0.020 inches (0.508 mm) below the maximum case length, the case mouth contacts the specialized internal mandrel during subsequent sizing cycles. This physical restriction prevents the brass from flowing forward, stopping the neck wall from thickening and keeping the case length stabilized below the maximum limit.

Key Features

• Patented X-Die Mandrel: Eliminates the need for repeated case trimming after an initial trim of 0.020 inches (0.508 mm) below maximum case length.
• Two-Die Configuration: Includes the X-Die Full-Length Sizing/Decapping Die (complete with decapping pin, expander ball, and mandrel) and a Standard Bullet Seating Die with an integrated roll crimper.
• Universal Compatibility: Standard 7/8"-14 thread fits most popular single-stage and progressive reloading presses.
• Custom Headspace Tuning: Allows users to customize case shoulder headspace to a specific rifle chamber by backing the die off one full turn and adjusting downward in 1/8 to 1/4 turn increments.

Product Specifications

• Manufacturer Brand: RCBS
• Model Number: 37212 (also designated as R37212)
• Calibre Compatibility: .223 Remington / 5.56×45mm NATO
• Die Thread: 7/8"-14
• Required Accessories: RCBS Shell Holder #10 (sold separately)
• Box Dimensions: Approximately 4.5 inches wide by 2.0 inches high
• Shipping Weight: 1.175 to 1.375 lbs (approximately 530 to 620 grams)

Who is the RCBS .223 Remington X-Die Full Length 2-Die Set for?

• High-volume .223 Remington target shooters — saves processing time by using this full-length reloading die set, which stops case stretch and eliminates repetitive trimming once bottleneck brass is initially trimmed to 0.020 inches (0.508 mm) below the maximum case length.
• Varmint hunters reloading .223 Remington ammunition — extends the service life of brass cases using this specialized RCBS .223 Remington X-Die Full Length 2-Die Set, which prevents neck growth by restricting brass flow when the case mouth contacts the mandrel inside the 7/8"-14 threaded die.
• Reloaders seeking to eliminate repetitive brass trimming steps — standardizes and stabilizes brass dimensions below SAAMI maximum limits after a single initial trim of 0.020 inches (0.508 mm), allowing this full-length reloading die set to bypass the trimming step in all subsequent reloading cycles.

Less suitable for: Owners of semi-automatic, pump-action, or tight-chambered firearms who require a specialized small-base sizer die to ensure reliable chambering, as standard full-length dies may not reduce the lower portion of the case sufficiently; it is also unsuitable for reloaders who process unlubricated cases (which will stick in these steel dies) or those who do not perform the mandatory initial trim of 0.020 inches (0.508 mm) below the maximum case length.