Lyman H&i Sizing Die .378

• .378 sizing diameter: This H&I sizing die is made for cast bullets that need a .378 final diameter, helping maintain the bullet-to-bore fit that supports consistent accuracy and cleaner performance.
• Body sizing operation: The die sizes the bullet body to a uniform diameter, which is essential when cast bullets vary slightly after casting and lubrication.
• Tapered mouth and hardened interior: Lyman’s H&I sizing die design helps guide bullets into the die smoothly and keeps them aligned, supporting a true cylindrical shape during sizing.
• 90° hole spacing: The improved hole layout makes lubrication easier to apply, including with harder bullet lubes that can be more difficult to work with in older designs.
• Steel construction: A steel sizing die stands up well to repeated bench use and gives reloaders a durable tool for regular cast-bullet production.

About the H&I Series

Lyman H&I sizing dies are part of the company’s long-established bullet-casting and reloading range, aimed at shooters who cast their own bullets and want tighter control over final bullet diameter. In Lyman’s lineup, these dies sit alongside lubricating and sizing equipment used to prepare cast bullets for rifle and pistol loading. Their role is straightforward but important: they bring bullets to a consistent finished diameter while supporting proper lubrication during the sizing process.

The series is built around practical workshop use. Improved 90° hole spacing is intended to make bullet lubrication easier, including with harder modern lubricants, while the tapered mouth helps start the bullet into the die smoothly. Lyman also uses a hardened interior to support alignment and preserve a uniform cylindrical shape as the bullet passes through. Because cast bullets often need careful diameter matching to a specific barrel, the H&I series is offered in many diameters for common rifle and handgun calibers. That makes these dies especially relevant for reloaders who tune ammunition for accuracy, reduced leading, and dependable chambering rather than relying on one-size-fits-all bullet dimensions.

About the Lyman H&i Sizing Die .378

The Lyman H&i Sizing Die .378 is a single body sizing die intended for cast bullets that need a final .378 diameter. In cast-bullet loading, correct bullet diameter is one of the main factors behind good bore fit, stable accuracy, and reduced fouling. This die gives the reloader a simple way to bring bullets to a repeatable finished size instead of working with the small variations that naturally occur during casting.

Its design is focused on smooth, consistent operation. The tapered mouth helps guide bullets into the die with less chance of shaving or misalignment, while the hardened interior supports a straight pass through the die so the bullet keeps a proper cylindrical form. Lyman’s 90° hole spacing also matters in practice because it helps lubricant flow more easily around the bullet, which is useful when working with harder lubes. For reloaders using a lubricator-sizer setup, that means less fuss at the bench and more consistent finished bullets.

This is a standard steel die with standard 7/8"-14 thread press compatibility, making it easy to integrate into common reloading setups. As a single-die solution for a specific bullet diameter, it suits reloaders who already know the exact size their rifle or handgun prefers and want a dedicated tool for repeatable cast-bullet preparation.

About Lyman

The Lyman Gun Sight Company began in 1878 in Middlefield, Connecticut. Over time, the company expanded from sight-making into a broader shooting and reloading business, and its product lines now include reloading dies, presses, bullet-casting equipment, and gun sights. That long involvement in both shooting accessories and handloading tools gives Lyman a strong connection to traditional bench reloading as well as practical field use.

Lyman acquired the Ideal reloading-tool business in 1925, a step that helped establish its place in the reloading category. The company’s tang and receiver sights still reflect principles from William Lyman’s original sight design, showing how its older product heritage continues to influence current offerings. Today, Lyman Products is headquartered in Middletown, Connecticut and remains focused on equipment and accessories for shooters and reloaders.

Main Features

• Manufacturer: Lyman
• Made in: USA
• Die operation: Body sizing
• Pack size: Single
• Die type: Standard
• Bushing: No
• Case type: Universal
• Sizing die material: Steel
• Material: Steel
• Adjustment: Standard
• Press compatibility: Standard 7/8"-14 thread
• Bullet Diameter (mm): 9.60 mm
• Bullet Diameter (inch): 378.00 inch

Warranty

Lyman covers this sizing die for 2 years. That warranty period suits a bench tool intended for regular reloading and cast-bullet sizing work.