The Redding 300 Rum Remington Ultra Magnum Competition Neck Die Set (Manufacturer Model Number: 58288) is a precision 3-die reloading system engineered for fire-formed .300 Remington Ultra Magnum brass. Designed for benchtop reloading presses using standard 7/8"-14 threaded die bodies, this set enables handloaders to control neck tension, manage cartridge concentricity, bump shoulders, and precisely seat standard .308-inch (7.62 mm) diameter bullets without overworking case brass.

Key Features

• Competition Bushing Neck Sizing Die (Part #56288): Utilises a free-floating sizing bushing (typically accommodating 0.334" to 0.342" bushings, sold separately) and an internal sliding sleeve to align the case before sizing. Features a micrometer-adjustable top graduated in 0.001" increments to precisely set the neck sizing length.
• Body Die (Part #75288): Resizes the case body and bumps the shoulder back 0.001" to 0.003" to restore headspace without contacting or modifying the case neck.
• Competition Bullet Seating Die (Part #55288): Features a precision-ground floating alignment sleeve that centres both the bullet and the case neck prior to seating, controlled by a non-click micrometer head graduated in 0.001" increments.
• Manual Tooling: Unpowered mechanical tooling with an approximate shipping weight of 0.9–1.1 kg, compatible with standard Australian single-stage and turret reloading presses.
• Shellholder Fit: Matches standard Redding Shellholder #6 (Part #11006 or Competition Shellholder #11606, sold separately).

Product Specifications

• Calibre: .300 Remington Ultra Magnum (.300 RUM)
• Bullet Diameter Compatibility: .308-inch (7.62 mm)
• Die Thread: Standard 7/8"-14
• Set Components: Competition Bushing Neck Sizing Die (#56288), Body Die (#75288), Competition Seating Die (#55288)
• Adjustment Graduations: 0.001" micrometer increments on neck sizing and bullet seating dies
• Compatible Bushing Sizes: 0.334" to 0.342" (sold separately)
• Total Tooling Weight: Approx. 0.9–1.1 kg (2–2.5 lbs)

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

• Extreme Long Range and F-Class Handloaders — Requires the precision micrometer head graduated in 0.001" increments to dial in consistent bullet seating depth and exact neck sizing length for bolt-action .300 Remington Ultra Magnum rifles.
• Precision Handloaders Seeking Maximum Brass Life — Employs standard 7/8"-14 threaded die bodies alongside separate neck sizing bushings and an isolated shoulder-bumping body die to minimize work-hardening on fire-formed .300 RUM cases.

Less suitable for: Semi-automatic actions or handloaders firing ammunition across multiple rifles sharing the same chambering, which require a full-length sizing die to guarantee chambering. Handloaders using unturned brass necks with variable wall thicknesses will also require an optional carbide expander ball kit to maintain uniform internal neck dimensions.