The Redding 300 Rum Remington Ultra Magnum Premium Die Set (Model 66288) is a precision 2-die reloading system engineered specifically for .300 Remington Ultra Magnum (.300 RUM) bottleneck rifle cartridges. Built with standard 7/8"-14 TPI mounting threads to fit standard single-stage and turret reloading presses, this American-made set returns fired brass to standard SAAMI factory dimensions and seats .308-inch (7.62 mm) diameter projectiles to precise depths.

Key Features:

• Free-Floating Carbide Expander Button: Integrated into the full-length sizing die to reduce friction, eliminate neck stretch, and remove the need for inside-neck lubrication while maintaining case concentricity.
• Bullet Seating Micrometer: Calibrated with direct 0.001-inch (0.025 mm) graduations on the seating stem for micro-adjustable control over bullet jump and overall cartridge seating depth.
• Full-Length Sizing Die: Resizes case necks, bodies, and shoulders simultaneously to ensure reliable chambering in factory and custom bolt-action rifles.
• Decapping Assembly: Built-in decapping pin removes spent primers during the initial sizing stroke.

Product Specifications:

• Cartridge Compatibility: .300 Remington Ultra Magnum (.300 RUM)
• Bullet Diameter: .308 in (7.62 mm)
• Die Thread Size: Standard 7/8"-14 TPI
• Required Shellholder: Redding #6 Standard Shellholder (#11006) or Competition Shellholder set (#11606) (sold separately)
• Packaged Shipping Weight: 0.65–0.75 kg (1.4–1.6 lbs)
• Package Contents: 1x full-length sizing die with carbide expander button, 1x bullet seating die with micrometer head, hex wrenches, instruction guide, and storage case

Who is the Redding 300 Rum Remington Ultra Magnum Premium Die Set for?

• Long-Range Competitive Shooters — Requires precise bullet jump adjustments down to 0.001-inch (0.025 mm) increments via the calibrated seating micrometer to optimize match-grade handloads using .308 in diameter projectiles for .300 RUM platforms.
• Big-Game Hunters — Needs consistent full-length resizing of .300 Remington Ultra Magnum brass back to SAAMI factory specifications on standard 7/8"-14 TPI presses to guarantee smooth feeding and chambering across various bolt-action hunting rifles.

Less suitable for: Handloaders seeking neck-only sizing without resizing the cartridge body for fire-formed brass (who require a dedicated 3-die neck sizing set), or those handloading alternative magnum calibres such as .300 Winchester Magnum, .300 WSM, or .300 Remington SAUM (which require calibre-specific die sets matching those distinct chamber dimensions).