Modular Sizing Die – Alpha Dasher

After carefully studying precision CNC machines and tooling, we designed the Modular Sizing Die with shallow tapers instead of threads, ensuring accurate centering and securing of the Solid Decapping Pin. This tapered geometry delivers unmatched concentricity and repeatability.

Our design also sizes slightly more at the base and less at the shoulder, which helps prevent extraction issues in properly sized rifle chambers. This geometry minimizes case runout and reduces brass overworking by avoiding excessive shoulder sizing.

Modular Sizing Die Assembly

• Modular Sizing Die Body: Built with standard 7/8 x 14 threads and made from 17-4 Stainless Steel, this die body features a Special Salt Bath Nitride finish for enhanced lubricity and performance.
• Universal Solid Decapping Pin: Constructed for high strength from 1144 Stress Proof Steel, the pin has a .058” nominal diameter tip to fit small primer flash-holes. You can adjust the pin tip protrusion by setting the wide mouth retaining clip position.
• Knurled ER11 Top Cap: With ¾ x 24 Threads, the Knurled ER11 Top Cap tightens into the die body, compressing the ER11 collet to secure the Decapping Pin or Expander Mandrel with the utmost concentricity.
• ER11 Collet: A commercially available ER11 collet secures various Decapping Pin and Expander Mandrel diameters.
• Taper Adapter: The Taper Adapter, located above the Neck / Shoulder Sizing Bushing, allows the Neck / Shoulder Sizing Bushing to float while the Knurled ER11 Top Cap seats the ER11 Collet into it, securing the Decapping Pin or Expander Mandrel.
• Neck / Shoulder Bushings: Available in various caliber-specific neck diameters, with .001” shims that let you adjust headspace without threading the die in or out, similar to traditional dies.

How to Set Up Your Short Action Customs Modular Sizing Die

• Clean the inside of the resizing die to remove debris. A .40 caliber plastic pistol brush and a 12-gauge shotgun patch work well for this.
• Assemble your Modular die as shown in the picture below.
• Raise the reloading press ram all the way up, then thread the resizing die into the press until the die body touches the shell holder. Lower the ram and thread the die down slightly to achieve a slight “cam over” with the press. Tighten the die body lock ring. For the Area 419 Zero Press, thread in the die about 1/8 of a turn after touching the shell holder.
• Using a headspace comparator, measure the shoulder of your fired brass to establish its headspace.
• Lubricate a clean, fired brass case and cycle it through the Modular Sizing Die with a smooth, consistent ram stroke.
• Measure your sized brass and compare it to the fired brass. For most shooting applications, reduce the headspace by .001”-.003”.
• To fine-tune headspace, adjust the resizing die body by threading it more or less into the press. We recommend using Redding Competition Shell Holders for additional adjustment. You can also adjust headspace by adding or removing .001″ shims between the “Neck/Shoulder Bushing” and the “Taper Adapter”.

What’s Included

• Modular Sizing Die Body
• Standard orange or grey lock ring
• ER11 Top Cap
• Taper Adapter
• ER11 Collet
• Decapping Pin
• (4) .001″ Shims
• Cardboard Shipping box