The Blackout 300 (designated as the  by the SAAMI and Blackout by the C.I.P.), also known as 7.62×35mm, is an intermediate cartridge developed in the United States by Advanced Armament Corporation (AAC) for use in the M4 carbine. Its purpose is to achieve ballistics similar to the 7.62×39mm cartridge or, even more similarly, the 7.92×33mm Kurz cartridge in an M4 while using standard M4 magazines at their normal capacities. Ammunition in .300 BLK cannot be used in a rifle chambered for 7.62×40mm Wilson Tactical. It is mainly derived from the .300 Whisper concept, but differs in having been submitted to the SAAMI.