The Redding Competition Upgrade PR-50 Hemispherical Metering Chamber (MPN: 03932) is a drop-in mechanical micrometer assembly engineered to convert an existing Redding Model 3BR Powder Measure to Precision Rifle competition specifications. It provides manual volumetric powder dispensing across a usable charging capacity of 15 to 100 grains, with an optimal consistency sweet spot between 35 and 75 grains. Designed specifically for smokeless propellants, the assembly measures approximately 50 mm in overall length and operates purely mechanically without the need for mains electricity or battery power.

Key Features

• Hemispherical Plunger Geometry: Built with a cup-shaped, curved plunger face rather than a standard flat cylinder. This design eliminates sharp internal 90-degree corners to prevent powder bridging and voids, facilitating uniform settle patterns when dispensing coarse extruded stick powders.
• Anti-Backlash Micrometer Adjustment: Integrates a precision-threaded micrometer drum that eliminates thread play, delivering repeatable volumetric charge adjustments across the 15 to 100 grain range.
• Direct Drop-In Fit: Replaces standard drums exclusively on Redding Model 3BR Powder Measure bodies without machining or permanent modifications.
• Mechanical Operation: Fully manual bench-mounted component requiring no electrical connections or external power sources.

Technical Specifications

• Device Type: Powder measure metering chamber assembly
• Manufacturer Part Number: 03932 (RED03932)
• Compatibility: Redding Model 3BR Powder Measures exclusively
• Usable Charge Capacity: 15 to 100 grains
• Optimal Sweet Spot Range: 35 to 75 grains
• Overall Assembly Length: Approximately 50 mm
• Approved Propellants: Smokeless powders (explicitly prohibited for black powder)
• Power Requirements: Manual mechanical operation

Who is the Redding Competition Upgrade PR-50 Metering Chamber for?

• Precision rifle competition shooters — requires precise charge consistency when loading medium-to-large rifle cartridges within the optimal 35 to 75 grains sweet spot using an upgraded powder measure metering chamber.
• Benchrest reloaders dispensing extruded stick powders — relies on the anti-bridging hemispherical cavity across a usable range of 15 to 100 grains to eliminate internal voids and maintain tight volumetric uniformity.

Less suitable for: Handgun or small-rifle handloaders requiring sub-15-grain loads where this chamber volume is too large to maintain tight consistency (a dedicated handgun or small-capacity metering chamber fits better), ultra-magnum cartridges exceeding 100 grains (an extreme-capacity powder measure fits better), or any dispensing involving black powder.