The Redding 56153 Competition Neck Sizing Die is engineered specifically for handloaders sizing fire-formed .300 Winchester Magnum cartridge brass. Built with a heat-treated, polished alloy steel body and standard 7/8"-14 reloading press threading, this die utilizes an internal, closely toleranced sliding sleeve that fully captures and aligns the case before the neck contacts the sizing bushing. By using a free-floating Redding neck sizing bushing (sold separately) and eliminating the need for an expander ball, the die minimizes case neck runout and prevents brass stretch while preserving the fire-formed dimensions of the cartridge shoulder and body.

Key Features

• Sliding Alignment Sleeve: Fully supports and centres the .300 Win Mag cartridge case prior to sizing, ensuring concentric neck-to-body alignment.
• Micrometer Neck Depth Control: Top-mounted micrometer with 0.001 in graduations enables precise adjustment of the bushing position to partially or fully size the case neck.
• Free-Floating Bushing Design: Sizing bushings self-centre directly on the case neck axis to prevent induced concentricity errors.
• Expander-Free Operation: Sizes case necks externally without drawing an expander button through the neck, preserving concentricity and preventing case lengthening.
• Standard Press Mounting: Threads directly into any standard 7/8"-14 single-stage or turret reloading press.

Specifications

• Manufacturer Part Number (MPN): 56153
• Calibre Compatibility: .300 Winchester Magnum (.308 in / 7.82 mm bullet diameter)
• Thread Interface: Standard 7/8"-14 threads
• Material: Heat-treated, polished alloy steel
• Adjustment Increment: 0.001 in micrometer graduations
• Shellholder Compatibility: Standard Redding #6 shellholder (#11006) or Competition Shellholders (#11606)
• Included Accessories: Standard decapping rod (accepts optional Carbide Size Button Kit #99407)
• Required Components: Redding neck sizing bushings (sold separately)

Who is the Redding Competition Bushing Neck Sizing Die for .300 Winchester Magnum for?

• Precision Long-Range Target Shooters — Loading fire-formed brass for .300 Winchester Magnum bolt-action rifles, where adjusting neck-sizing depth via the 0.001 in micrometer graduations preserves the cartridge's exact shoulder fit to the chamber.
• F-Class and Benchrest Handloaders — Using a competition neck sizing die with standard 7/8"-14 threading to eliminate expander-button drag and control neck tension precisely using interchangeable bushings, minimizing bullet runout across large-capacity .300 Win Mag cases.

Less suitable for: Semi-automatic, pump, or lever-action rifles requiring SAAMI-standard body dimensions for reliable feeding, as well as cases that have expanded through repeated high-pressure firings; handloaders in these situations require a full-length sizing die or a dedicated body die to bump the shoulder and resize the case body.