8.6mm Blackout (8.6×43 mm), sometimes referred to as 8.6 BLK,[1] is a centerfire rifle cartridge developed by the firearms manufacturer Q, LLC.

The only required modification to convert an existing .308 Winchester-chambered rifle to 8.6mm Blackout is the replacement of the barrel.

[7] The 8.6 Blackout shares the same case head and bolt diameter as its parent cartridge, 6.5mm Creedmoor.

8.6 Blackout fits in standard, unmodified .308 Winchester or 6.5 Creedmoor magazines with no effect on capacity.

[9] The "fast" twist rate 8.6mm Blackout is designed for was intended to create better bullet expansion and more terminal energy transferred to the target through "Blender effect".