.400 Legend

The .400 Legend, also called 400 LGND (10x42mmRB), is a SAAMI-standardized straight-walled intermediate rifle cartridge developed by Winchester Repeating Arms. The cartridge was designed for use in American states that have specific regulations for deer hunting with straight-walled centerfire cartridges. It is designed for deer hunting out to a maximum effective range of 300 yd.

Overview
The .400 Legend is suitable for use in AR-15 type semiautomatic rifles.

History
On April 14, 2023, Winchester Ammunition announced the .400 Legend. The Sporting Arms and Ammunition Manufacturers' Institute (SAAMI), the U.S. firearms and ammunition industry's technical standards-setting organization, announced the acceptance of the new cartridge and chamber standard on January 15, 2023.

The .400 Legend was preceded by the Winchester Model 1910 .401 Winchester Self-Loading cartridge, and in 2014 by the .400 AR wildcat cartridge designed for the AR-15–style rifle.

Technical Drawing
Link to SAAMI Cartridge and chamber drawings.

Usage
The .400 Legend cartridge is engineered for deer hunters requiring a modern straight-walled cartridge that is more powerful and has greater effective range than the .350 Legend.

State legislation
.400 Legend also addresses a rapidly growing market segment known as "straight-wall-cartridge-compliant" deer-hunting states. A growing number of states that previously restricted deer hunting to limited-range slug guns or muzzleloading firearms are now allowing rifles chambered in straight-walled centerfire cartridges.

The .400 Legend was designed for deer hunting in states that have specific regulations requiring straight-walled cartridges for use on deer, such as Ohio, Iowa, Indiana public land, and the Southern Lower Peninsula region of Michigan. Illinois also allows straight-walled cartridges if used with a pistol or a single-shot rifle. The pistol must be a centerfire revolver or centerfire single-shot handgun of .30 in caliber or larger with a minimum barrel length of 4 in inches. Single-shot rifles in those specified calibers became legal on January 1, 2023.

Ohio's Deer Hunting Regulations allow the use of a straight-walled rifle cartridge with a minimum caliber of .357 in.

Indiana regulations actually do not mandate a straight-walled cartridge. When hunting on private land, virtually all centerfire cartridges with a bullet diameter of at least .243 in (6.2 mm) are legal. On public land, state regulations mandate minimum and maximum case lengths of 1.16 inches (29 mm) and 1.8 inches (46 mm) respectively, plus a minimum bullet diameter of .357 in (9.1 mm), but do not mandate a specific case shape. While many straight-walled cartridges meet Indiana requirements, some bottlenecked cartridges also do so, with a notable example being the .458 SOCOM.