Blackout-300. The Windham Weaponry SRC “sight ready carbine”, now available in 300 Blackout, was created for those AR shooters who intend to add their own aftermarket sights, scopes or optics, and want a rifle that offers the option of not purchasing factory sights. The SRC 300 Blackout offers all the Windham Weaponry quality with the flexibility of front and rear same plane Picatinny Rails. 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.