The 350 Legend cartridge was introduced by Winchester Ammunition at SHOT Show 2019. It’s a .358-caliber straight-walled rebated rim AR-15 cartridge that became quite popular with many companies now offering firearms chambered in 350 Legend. Well, looks like its younger but bigger brother is on the way. SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) have published cartridge and chamber drawings of a not yet announced round called 400 Legend (400 LGND). Let’s take a closer look.

SAAMI @ TFB:

• SAAMI Specs of the 360 Buckhammer (360 BHMR) Cartridge
• SAAMI Announces Suppressor Thread & Socket Drawings
• SAAMI Publishes 30 Super Carry Cartridge Specs
• 7mm PRC (Precision Rifle Cartridge) SAAMI Specs Released

The 400 Legend is a 40-caliber straight-walled rebated rim cartridge. The rim diameter is .422″, identical to that of the 6.8 Remington SPC, and the overall length is 2.26″ which means this cartridge is also designed to be used in AR-15 pattern firearms. So an AR chambered in 400 Legend should be able to use 6.8 Rem SPC bolts and maybe 6.8 SPC or 6.5 Grendel magazines. The 400 Legend cartridge operates at a Maximum Average Pressure (MAP) of 45,000 psi and is capable of pushing a 215-grain bullet to a muzzle velocity of 2,230 fps per SAAMI specs.

400 Legend chamber drawings

I suppose like the 350 Legend, the 400 Legend is primarily designed to be used as a hunting cartridge in states where only straight-walled cartridges are allowed for deer hunting. Where I think this cartridge could also shine is the suppressed use with heavy subsonic bullets. It should be possible to load this cartridge with 300-grain or heavier projectiles to its maximum COAL while still leaving enough powder room in the case to get muzzle velocities of about 1050 fps. Let us know what you think in the comments section.

Pictures used in this article are screenshots from the SAAMI cartridge and chamber drawings of the 400 Legend. To download the full SAAMI document, click HERE.