The Redding .300 Remington Ultra Magnum Neck Sizing Die (MPN: 81288) is a dedicated reloading die engineered to resize only the cartridge case neck of fired .300 RUM brass while leaving the fire-formed body and shoulder untouched. Designed for standard 0.308-inch diameter bullets, this tool decaps spent primers and expands the inner case neck to uniform tension in a single press stroke. By eliminating repeated full-length body sizing, it reduces brass work-hardening and preserves fire-formed chamber concentricity for bolt-action rifles.

Key Features

• Neck-Only Resizing: Sizes the neck area without altering the fire-formed body dimensions or shoulder angle of fired .300 RUM brass.
• Integrated Decapping and Expansion: Features a decapping rod assembly and expander sizing button to decap and set inner neck tension simultaneously.
• Extended Brass Life: Minimises work-hardening on expensive magnum cartridge cases to increase reloading cycles.
• Universal Press Mounting: Fitted with industry-standard 7/8"-14 threads and includes a Sure-Loc split lock ring for secure, repeatable installation across standard reloading presses.

Specifications

• Calibre Compatibility: .300 Remington Ultra Magnum (.300 RUM)
• Bullet Diameter: Standard 0.308-inch bullets
• Die Thread Size: Standard 7/8"-14 thread
• Required Shellholder: Standard #6 shellholder (sold separately)
• Packaged Weight: Approximately 0.25 kg (250 g)
• Packaged Dimensions: Approximately 14.0 cm (L) × 6.0 cm (W) × 4.0 cm (H)
• Power Requirement: None (manual reloading press tool)

Who is the Redding .300 RUM Neck Sizing Die for?

• Precision Bolt-Action Handloaders — Reloaders tailoring match ammunition for a single dedicated bolt-action rifle require this 300 RUM neck sizing die with standard 7/8"-14 thread fitment to preserve the exact fire-formed body dimensions of their specific chamber for concentric bullet alignment.
• Long-Range Magnum Hunters — Shooters managing high-capacity .300 Remington Ultra Magnum (.300 RUM) brass use this 0.25 kg steel neck die to eliminate work-hardening across the case body, significantly prolonging the service life of expensive magnum cartridge cases.

Less suitable for: Semi-automatic, pump-action, or lever-action firearms, as well as cases fired across multiple different rifles of the same calibre; brass that has stretched after 3 to 5 firings requires a full-length sizing die or a dedicated body die to push the shoulder back and maintain reliable feeding.