8.6 mm Blackout Subsonic

The 8.6mm Blackout, also known as 8.6 BLK, is a modern cartridge specifically engineered with subsonic performance in mind, making it one of the most suitable calibers for suppressed shooting. Developed by Q LLC as a larger-caliber counterpart to the 300 Blackout, the 8.6 BLK is based on a shortened and necked-down 6.5 Creedmoor case, allowing it to fire heavy .338-caliber bullets in subsonic and supersonic configurations. Its design excels in short barrels (typically 12" or less) and suppressed platforms, where it delivers exceptional energy retention and terminal performance even at subsonic velocities.

For subsonic loads, the most popular projectiles are 285–350 grain bullets, including expanding solid copper and fracturing types like those from Gorilla, Maker, and Lehigh Defense. Powder choices often include fast-to-medium burn rate options like Hodgdon H110, IMR 4227, and Vihtavuori N110. These powders help maintain consistent pressure and velocity in the 1,000–1,050 fps range, ideal for quiet and effective shooting. Due to the case’s capacity and projectile weight, proper load density and crimping are essential to avoid erratic ignition or bullet setback.

The 8.6 BLK’s optimized twist rates (often 1:3 to 1:4 inches) are critical to stabilizing heavy bullets subsonically, and they also enhance terminal effects via yaw and tumble. Reloaders should take special care to use accurate case conversion practices and stay within published pressure specs, as the cartridge is still relatively new. Nonetheless, for subsonic use with maximum suppression efficiency and hard-hitting performance, the 8.6mm Blackout sets a new benchmark.