The Lyman Single Cavity Rifle Bullet Mould #457671 .45 Caliber 475 Grain Round Nose Gas Check (Manufacturer Part Number: LY-M40671, also catalogued as 2640671) is a precision-engineered casting tool designed for handloaders who demand extreme accuracy and consistency. Machined from solid leaded-steel blocks, this mould undergoes a specialised heat-treatment process that results in a deep blue finish. This thermal treatment significantly reduces the break-in time compared to standard iron moulds, allowing shooters to cast high-quality projectiles almost immediately. The mechanical design features a gas check base, which allows the cast bullets to be driven at higher velocities without causing excessive lead fouling in the rifle barrel.

Key Features:

• Premium Steel Construction: Crafted from solid leaded-steel and heat-treated to a deep blue finish, reducing break-in time by up to 50 percent.
• Gas Check Design: Casts a bullet with a gas check base, enabling handloaders to achieve higher velocities while preventing bore leading.
• Precision Alignment: Equipped with hardened steel alignment pins that ensure the block halves close perfectly every time for round, seamless bullets.
• Flat Ground Sprue Plate: Features a solid steel sprue plate, ground flat and held firmly with tempered steel spring washers and screws for clean cuts.
• Single Cavity Efficiency: The single-cavity configuration allows for precise temperature control, resulting in highly uniform bullet weights and dimensions.

Product Specifications:

• Brand: Lyman
• Model Number: LY-M40671 / 2640671
• Mould Number: #457671
• Calibre: .45 Calibre
• Nominal Cast Diameter: .458" to .459" (depending on alloy mixture)
• Bullet Weight: 475 Grains (nominal weight calculated using Lyman #2 alloy)
• Bullet Profile: Round Nose (RN) with Gas Check (GC)
• Capacity: Single Cavity
• Required Handles (Sold Separately): Requires Lyman Double Cavity Mould Handles to fit this block size.
• Recommended Sizing Top Punch (Sold Separately): Lyman Top Punch #374.
• Power Requirements: None. This is a manual, non-powered mechanical tool. No 240V electrical connection, SAA certification, or Australian power plugs are required.

Who It Is For:

This Lyman bullet mould is specifically designed for Australian handloaders, competitive target shooters, and classic rifle enthusiasts who reload for the .458 Winchester Magnum or heavy-calibre single-shot rifles (including classic black powder and modern cartridge single-shots). It is ideal for those who require heavy, gas-checked projectiles capable of handling higher velocities without sacrificing accuracy. Because lead casting involves melting metals at high temperatures, users in Australia should always operate this equipment in a well-ventilated space and wear appropriate personal protective equipment (PPE) to ensure a safe reloading environment.