Lyman H&i Sizing Die .400

• .400 sizing diameter: Sizes cast bullets to .400 for consistent fit in compatible bores, helping support uniform pressure, cleaner shooting and better practical accuracy.
• Body sizing operation: This H&I die is built to size the bullet body cleanly and evenly, which helps maintain a true cylindrical shape for smoother lubrication and more consistent results on the loading bench.
• Steel construction: The steel die body stands up to repeated use and keeps its dimensions well over time, making it a dependable choice for regular cast-bullet work.
• Standard 7/8"-14 compatibility: The die fits presses with the common 7/8"-14 thread, so it integrates easily into established reloading setups without special adapters.
• Made in USA: Domestic manufacture and Lyman’s long focus on reloading tools make this die a practical fit for reloaders who want established support and familiar component standards.

About the Series Series

Lyman H&I Sizing Dies are part of the company’s long-running cast-bullet tooling range, aimed at reloaders who want to size and lubricate bullets to a controlled final diameter. Within Lyman’s bullet-casting lineup, this series sits alongside the brand’s lubricating and sizing equipment and is intended for shooters who cast their own bullets for handgun and rifle use. The purpose of the series is straightforward: bring cast bullets to the correct diameter for the application while supporting proper lubrication during the same workflow.

A defining characteristic of the series is its focus on practical bench use. Lyman improved sizing dies use 90° hole spacing to make bullet lubrication easier, including with harder modern lubricants. They also feature a tapered mouth and a hardened interior, details that help guide the bullet into the die and support a more uniform cylindrical result. The H&I format is widely used by cast-bullet reloaders because it offers a simple, caliber-specific way to match bullet diameter to the firearm, which is one of the key steps in getting reliable accuracy and controlled fouling from cast loads.

About the Lyman H&i Sizing Die .400

The Lyman H&i Sizing Die .400 is a single body sizing die intended for cast bullets that need a final diameter of .400. In practical terms, that makes it relevant for reloaders working with bullet designs and cartridges where correct bullet fit is especially important to both accuracy and barrel condition. Cast bullets that are too large can chamber poorly or create excess resistance, while bullets that are too small may not seal the bore as effectively. A dedicated sizing die helps bring that dimension under control.

This model uses a steel sizing die body with a standard adjustment layout and fits presses with a 7/8"-14 thread, so it works naturally within common reloading setups. As part of Lyman’s H&I system, it is designed for use in a cast-bullet sizing and lubrication process rather than as a conventional cartridge case die. That distinction matters in use: the goal is not case preparation, but producing bullets with a more consistent finished diameter and shape before loading. For reloaders who cast in volume, that consistency can make seating feel more uniform and can help loads behave more predictably on target. The result is a simple, purpose-built tool for bullet sizing work where dimensional control matters more than added complexity.

About Lyman

The Lyman Gun Sight Company began in 1878 in Middlefield, Connecticut, and the business grew from William Lyman’s original sight design. Over time, the company expanded well beyond sights and became closely associated with the broader handloading and shooting market. Lyman acquired the Ideal reloading-tool business in 1925, a step that helped establish its long-standing place in reloading equipment.

Today, Lyman Products is headquartered in Middletown, Connecticut and makes equipment and accessories for shooting and reloading. Its range includes reloading dies, presses, bullet-casting equipment, and gun sights, which makes the brand especially familiar to reloaders who want related tools from one established maker. That background is directly relevant to a product like the H&I sizing die, which sits within Lyman’s long-developed cast-bullet and bench-tool lineup.

Main Features

• Manufacturer: Lyman
• Country of Manufacture: USA
• Die Operation: Body sizing
• Pack Size: Single
• Die Type: Standard
• Bushing: No
• Case Type: Universal
• Sizing Die Material: Steel
• Adjustment: Standard
• Press Compatibility: Standard 7/8"-14 thread
• Bullet Diameter: 10.16 mm
• Bullet Diameter (inch): 400.00 inch

Warranty

Lyman provides a 2-year warranty for this sizing die. That period suits a bench tool intended for repeated reloading use and adds clear manufacturer-backed coverage with a stated term.