The Hornady Lock-N-Load Cartridge Gauge .357 Magnum (MPN: 380703) is a precision-machined handgun cartridge headspace gauge designed to verify that handloaded ammunition and resized brass conform to standard SAAMI chamber dimensions. Operating as a mechanical drop-in go/no-go inspection tool, it allows reloaders to instantly identify out-of-spec case diameters, improper overall lengths, insufficient crimping, or flared case mouths prior to firing. Machined from hardened steel to replicate minimum factory chamber tolerances, this passive benchtop tool prevents chambering failures, feeding jams, and cylinder-binding issues across field and target shooting disciplines.

Key Features

• SAAMI-Reamed Chamber Tolerances: Precision-cut internal dimensions replicate standard SAAMI factory chambers, verifying overall length, case diameter, and rim seating in a single drop-in test.
• Machined Hardened Steel Construction: Built from durable, wear-resistant steel designed to withstand repetitive benchtop case checks without dimensional erosion.
• Instant Go/No-Go Verification: Machined surface steps clearly show whether brass sits flush with the gauge face or protrudes, indicating the immediate need for trimming, sizing, or deburring.
• Mechanical Simplicity: Functions entirely as a passive, unpowered tool requiring no batteries, calibration dials, or electronic maintenance.

Specifications

• Calibre Compatibility: .357 Magnum (.357" bullet diameter specification)
• Material: Precision-machined hardened steel
• Capacity: Single-cartridge capacity (manual insertion and extraction)
• Packaged Weight: Approximately 0.33 lbs (~150 g)
• Power Requirements: None (manual, passive mechanical tool)

Who is the Hornady Cartridge Gauge 357 Mag for?

• Handloaders loading .357 Magnum ammunition for revolvers — ensures uniform clearance across cylinder chambers by using a dedicated .357 Magnum calibre compatibility profile to catch bulging cases or high rims before they bind cylinder rotation.
• Reloaders manufacturing .357 Magnum rounds for lever-action rifles — provides rapid single-cartridge capacity pass/fail quality control at a compact 0.33 lbs packaged weight, preventing expanded brass from causing stubborn cycling stops or extraction failures in tubular magazine actions.

Less suitable for: Handloaders processing .38 Special brass, as differing case length steps make this gauge incompatible; shooters inspecting .38 Special require a dedicated cartridge gauge reamed specifically to .38 Special case dimensions.