7.62 x 39 (.308) Russ. Subsonic

The 7.62×39mm Russian cartridge, typically loaded with .311" diameter bullets but also compatible with .308" bullets in some firearms, can be effectively adapted for subsonic use—especially in suppressed platforms. Originally developed for military rifles like the AK-47, its moderate case capacity makes it well-suited for subsonic loads when paired with heavy bullets and appropriate powders. Most subsonic loads in this caliber use bullets in the 180–220 grain range and fast-burning powders such as Trail Boss, IMR 4227, Hodgdon CFE BLK, or Vihtavuori N320, which provide sufficient pressure for reliable ignition while keeping velocities below the sound barrier (~1,050 fps).

Subsonic performance in semi-auto rifles like the SKS or AK platforms can be inconsistent without gas system modification, making bolt-action rifles or manually-cycled semi-autos a better match. Reliable cycling may not be achievable without tuning, especially at such low pressures. Careful attention is needed to ensure complete powder burn and avoid squibs, particularly when loading to low case fill levels. Crimping and bullet seating depth are critical for consistency and safety. While not a powerhouse in subsonic form, 7.62×39 subsonic loads can be highly effective for training, quiet hunting, or suppressed shooting applications. Always start with published data when available and confirm performance with a chronograph.