Modular Sizing Die – 6 ARC

After extensive studies in precision CNC machining and tooling, we designed the Modular Sizing Die to use shallow tapers rather than threads for centering and securing the Solid Decapping Pin. This tapered geometry ensures optimal concentricity and repeatability.

Our design for cartridge sizing geometry increases sizing at the base and reduces it at the shoulder, compared to most resizing dies. This sizing pattern minimizes extraction issues in properly sized rifle chambers, reduces case runout, and prevents overworking the brass by avoiding excessive shoulder sizing.

Modular Sizing Die Assembly

• Modular Sizing Die Body: Standard 7/8 x 14 threads, 17-4 Stainless Steel, with a Salt Bath Nitride finish for added lubricity and performance.
• Universal Solid Decapping Pin: Built from 1144 Stress Proof Steel for strength, with a .058” nominal diameter pin tip for small primer flash-holes. You can adjust the Solid Decapping Pin’s protrusion by repositioning the wide-mouth retaining clip.
• Knurled ER11 Top Cap: ¾ x 24 Threads secure the ER11 Top Cap into the die body, compressing the ER11 collet to ensure precise concentricity for the Decapping Pin or Expander Mandrel.
• ER11 Collet: A commercially available collet that can hold various Decapping Pin and Expander Mandrel diameters.
• Taper Adapter: When threaded, the Knurled ER11 Top Cap seats the ER11 Collet into the Taper Adapter, securing the Decapping Pin or Expander Mandrel. Positioned above the Neck/Shoulder Sizing Bushing, the Taper Adapter allows the bushing to float.
• Neck / Shoulder Bushings: Available in a range of caliber-specific neck diameters. You can use special .001” shims above the bushing to adjust headspace without threading the die in or out, similar to traditional dies.

Setting Up Your Short Action Customs Modular Sizing Die

• Clean the inside of the resizing die to remove debris. We recommend a .40 caliber plastic pistol brush with a 12-gauge shotgun patch for this.
• Assemble your Modular Die following the example in the image below.
• With the reloading press ram fully raised, thread the resizing die into the top of the press until the die body contacts the shell holder. Lower the ram slightly and thread the die down to achieve a slight “cam over” with the press. Then tighten the die body lock ring. If using the Area 419 Zero Press, thread in your die about 1/8″ after it contacts the shell holder.
• Use a headspace comparator on the shoulder of the brass to establish the fired brass headspace.
• Lubricate a clean, fired brass case and cycle it through the Modular Sizing Die using a smooth, consistent stroke.
• Measure the sized brass and compare it to the fired brass. We recommend a headspace reduction of .001”-.003” for most applications.
• To adjust headspace, either thread the die body in more or less or use Redding Competition Shell Holders. You can also modify headspace by adding or removing custom .001″ shims supplied with your die between the “Neck/Shoulder Bushing” and the “Taper Adapter.”

What’s in the Package

• 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