The Redding Competition Seating Die (Model 55153) is a precision handloading tool engineered specifically for straight-line bullet seating in .300 Winchester Magnum cartridges. Built from heat-treated, precision-ground steel, this die utilises an internal sliding alignment sleeve that captures and centres both the cartridge case and 0.308-inch diameter bullet before seating begins. A floating seating stem guides the bullet axially without inducing tilt, minimising bullet runout. The top-mounted micrometer provides continuous, non-clicking adjustments calibrated in 0.001-inch increments with a resettable zero mark, allowing handloaders to accurately tune and repeat cartridge overall length (COAL).

Key Features

• Straight-Line Alignment Sleeve: Fully supports and aligns the .300 Winchester Magnum case and bullet prior to seating to eliminate concentricity runout.
• Floating Seating Stem: Ground to close tolerances, the seating stem floats on a cushion of air to seat bullets straight without tilting the projectile.
• Micrometer Depth Control: Calibrated in precise 0.001-inch increments to provide repeatable bullet seating depths relative to rifle lands.
• Standard Press Compatibility: Features standard 7/8"-14 reloading threads to fit standard single-stage, turret, and progressive presses.
• Heat-Treated Steel Construction: Machined from hardened steel for high wear resistance and long-term dimensional stability.

Product Specifications

• Calibre Compatibility: .300 Winchester Magnum
• Bullet Diameter: 0.308 inch
• Thread Size: Standard 7/8"-14
• Adjustment Increments: 0.001 inch (micrometer top)
• Shellholder Compatibility: Redding #6 standard or #11606 Competition Shellholder (sold separately)
• Standard Seating Stem: Part #55030 (standard tangent/secant ogives)
• Material: Heat-treated, precision-ground steel
• Operation: Manual, mechanical reloading tool

Who is the Redding Competition Seating Die for .300 Winchester Magnum for?

• Long-Range Target and F-Class Competitors — Requires the 0.001-inch micrometer increments and straight-line sleeve alignment of this competition bullet seating die to precisely control seating depth and eliminate runout on 0.308-inch projectiles.
• Precision Long-Range Hunters — Relies on the 0.001-inch depth adjustments and standard 7/8"-14 press threading of this competition seating die to develop consistent, accurate handloads for .300 Winchester Magnum hunting rifles.

Less suitable for: Handloaders seating other .30-calibre cartridges (such as .308 Winchester or .300 WSM), who require a cartridge-specific seating die; operations requiring heavily compressed powder loads, which can disrupt the sliding sleeve mechanism; or applications requiring a crimped case mouth, which require a dedicated, separate crimping die.