The Hornady Lock-N-Load Modified Case (MPN: A7X57) is a dedicated measuring accessory engineered for handloaders working with the 7x57mm Mauser (7mm Mauser) cartridge. Designed to attach directly to Hornady Lock-N-Load Overall Length (O.A.L.) Gauges (Straight or Curved models), this brass case allows handloaders to determine precise cartridge base-to-ogive clearance and bullet jump to the rifling lands. Manufactured to factory SAAMI external dimensions with an approximately 57 mm case length, it ensures smooth chambering in standard 7x57 Mauser rifle chambers.

Key Features

• Threaded Base: The case head is drilled and tapped with fine precision threading to mate directly with Hornady Lock-N-Load O.A.L. Gauges.
• Oversized Case Mouth: The neck is precisely opened by approximately .002 inches (0.05 mm) to allow standard .284 inch (7mm) projectiles to slide freely with zero friction while maintaining concentric alignment.
• Bench-Rest Accuracy: Enables overall length and bullet seating depth measurements accurate to within .001 inches (0.025 mm) when used with an O.A.L. gauge and dial or digital calipers.
• SAAMI External Sizing: Sized to factory SAAMI specifications to chamber reliably in production 7x57 Mauser rifles.

Product Specifications

• Brand: Hornady
• Model / MPN: A7X57 (A-Series)
• Calibre Compatibility: 7x57mm Mauser / 7mm Mauser
• Bullet Diameter Compatibility: .284 in (7mm)
• Neck Expansion: .002 in (0.05 mm) over standard SAAMI specification
• Measurement Tolerance: Accurate to within .001 in (0.025 mm) when paired with a caliper and gauge tool
• Packaged Dimensions: Approximately 138.4 mm × 50.8 mm (5.45 in × 2.0 in)
• Operation: Manual mechanical measuring tool (non-powered)

Who is the Hornady Lock-N-Load Modified Case for 7x57 Mauser for?

• 7x57mm Mauser handloaders — needing to measure true base-to-ogive dimensions and throat engagement using standard .284 in (7mm) projectiles with a reloading modified cartridge case featuring a .002 inch (0.05 mm) expanded neck.
• Precision rifle reloaders — aiming to eliminate bullet seating variance down to a .001 inch (0.025 mm) measurement accuracy limit when handloading for standard 7x57mm Mauser chambers.

Less suitable for: Handloaders working with alternate 7mm cartridges (such as 7mm-08 Remington or 7mm Remington Magnum), or shooters using custom, tight-neck, or heavily fire-formed wildcat chambers where standard SAAMI brass introduces dimensional play; these applications require calibre-specific modified cases or custom modified cases manufactured from the shooter's own fire-formed brass.