.351 Win. SL Load Data & Reloading Guide

The .351 Winchester Self-Loading (SL) cartridge was introduced in 1907 alongside the Winchester Model 1907 semi-automatic rifle. Its development responded to the demand for a civilian semi-automatic rifle that could deliver more power than earlier models, making it suitable for medium-sized game hunting and home defense.

Technically, the .351 Win. SL is a rimless, straight-walled cartridge that uses a base diameter of 0.381 inches and a case length of 1.91 inches. Originally loaded with a jacketed soft point bullet, it was designed to maintain its shape and ensure consistent feeding in semi-automatic actions. Typical bullet weights for factory loads were around 180 grains, reaching muzzle velocities of approximately 1,850 feet per second. This provided respectable energy levels and adequate performance for its designated role in firearms of the time.

The ballistic performance of the .351 Win. SL makes it suitable for short to medium-range applications, particularly appropriate for hunting smaller deer and similar-sized game. Its straight-walled case aids in reliable cycling in semi-automatic platforms, offering shooters a fast follow-up shot capability. Although less common today, it maintains a following among historical firearms enthusiasts and hunters who appreciate classic calibers.

For reloaders, the .351 Win. SL provides an opportunity to recreate period-correct ammunition which can be personalized for specific firearms. Reloaders benefit from the availability of modern components which can optimize performance by fine-tuning powder charge and bullet choice. Given its limited commercial availability, reloading can ensure sustained use and performance improvements, preserving the shooting experience of vintage semi-automatics.