What thread size does the Hornady 390751 Large Primer Pocket Reamer Head use for installation?

The Hornady 390751 features an industry-standard 8-32 male thread interface. This allows it to thread easily into a wide range of compatible equipment, including Hornady hand tool handles, the Lock-N-Load Case Prep Trio, and the Power Case Prep Center.

Can I use this large reamer head on 5.56x45mm NATO or .223 Remington military brass?

No, this specific model (390751) is engineered exclusively for large Boxer primer pockets with a nominal diameter of 0.210 inches (5.33 mm), commonly found on 7.62x51mm NATO or .308 Winchester brass. For small primer pockets measuring 0.175 inches (4.45 mm) like 5.56mm cases, you must use the Hornady Small Reamer Head model 390750 instead.

Does this reamer head require any electrical power or Australian SAA/RCM certifications?

No, the Hornady 390751 is a passive mechanical tool head made from hardened steel and contains no internal electronics or motors. Therefore, it does not require mains power, batteries, or any Australian electrical safety certifications like SAA or RCM.

How should I store and maintain this hardened steel reamer head to prevent corrosion during humid Australian conditions?

Constructed from durable hardened steel, the reamer head is built for longevity on your reloading bench. To protect it from rust or moisture during storage in outback or humid coastal regions, apply a light coat of gun oil or case lube—such as the Hornady Case Lube Pad—after use.

Does the Hornady 390751 cut away brass or does it swage the primer pocket?

This specific tool is designed to cut and ream material away from the primer pocket mouth, effectively removing stubborn stake, ring, or stab crimps found on surplus military brass. If you prefer to displace brass without cutting metal, a dedicated primer pocket swaging tool would be an alternative choice.

Large Primer Reamer - Hornady 390751

The Hornady Large Primer Pocket Reamer Cutter Head (Model #390751) is a hardened steel case preparation accessory designed to cut away military primer crimps on large Boxer-primed cartridge cases. Military-surplus brass commonly features ring, stake, or stab crimps that prevent standard replacement primers from seating correctly. This reamer removes the crimped brass edge to ensure smooth, uniform primer seating without crushing or deforming new primers. Constructed with a standard 8-32 male thread, the cutter head can be threaded directly into manual handles or motorized case preparation centers.

Key Features

Crimp Removal: Precision-cuts factory stake and ring crimps from military brass mouths to allow consistent primer seating.
Universal 8-32 Threading: Features a standard 8-32 male thread interface compatible with the Hornady Lock-N-Load Case Prep Trio, Power Case Prep Center, Hornady Universal Hand Tool, and standard rotary drill adapters.
Durable Construction: Made from hardened tool steel to maintain cutting edge sharpness across high-volume brass processing sessions.
Versatile Operation: Operates manually when attached to hand handles or powered via rotary case prep stations.

Specifications

Manufacturer Part Number (MPN): 390751
Primer Pocket Compatibility: Large Boxer primer pockets (nominal 0.210 in / 5.33 mm diameter)
Thread Interface: Standard 8-32 male thread
Material: Hardened steel
Power Requirements: Non-powered mechanical attachment

Who is the Hornady Large Primer Pocket Reamer Head for?

Reloaders processing surplus military brass — requires a dedicated large primer pocket reamer head sized for nominal 0.210 in (5.33 mm) diameter pockets to cleanly remove crimps from once-fired 7.62x51mm NATO and .308 Winchester cases.
Sporting shooters reloading large-primer military cartridge cases — utilizes an 8-32 male thread interface to fit standard motorized case prep centers or manual handles for processing calibres such as .30-06 Springfield and .45 ACP military brass.

Less suitable for: Processing small-primer cartridge cases with nominal 0.175 in (4.45 mm) diameter pockets (such as 5.56x45mm NATO or .223 Remington); reloaders working with these calibres require a small primer pocket reamer head or a dedicated bench-mounted primer pocket swaging tool.

SKU	HN102718LP
Model #	390751
Brand	Hornady
Shipping Weight	0.1000kg

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Hornady 390751 Large Primer Pocket Reamer Steel 8 32 Thread

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