8.6mm Blackout (8.6×43 mm), also sometimes referred to as 8.6 BLK, is a centerfire rifle cartridge developed by the firearms manufacturer Q which is famous for Honey Badger rifles.
The 8.6 Blackout was designed to be used for hunting with both subsonic and supersonic ammunition.
It utilizes a shortened case from the 6.5mm Creedmoor necked up to an 8.6 mm caliber or .338 as we know. Projectile and designed for use in bolt action rifles or as a caliber conversion for AR10 and AR-308 rifles.
Unlike 300BLK with 1:8 twist rate the 8.6 Blackout has been designed for barrels using a 76 mm or 102 mm (1:3 in or 1:4 in) twist rate and bullet weights between 10.4–14.6 g (160–225 gr) for supersonic loads and 18.5–22.7 g (285–350 gr) for subsonic loads.
The only required modification to convert an existing .308 chambered rifle to 8.6mm Blackout is the replacement of the barrel. All other components of a standard AR10/AR308 rifle are interchangeable. Modifications to the operating system such as the buffer, buffer spring and gas system may be made in order to optimize the functionality of the firearm. 8.6 Blackout utilizes standard, unmodified AR10 .308 / 6.5 Creedmoor magazines at standard capacity.