1102171421a November 2, 2017 at: 1500 × 844 In: .300 Blackout vs. 9x39mm: Russia’s Subsonic Brute [Modern Intermediate Calibers 026.1] ← Previous Next → Left to right: 7.62×39, 9.3×62, 9×39, 5.45×39, .300 Blackout, .223 Remington. The 9x39mm combines the bore diameter of the 9.3×62 and similar rounds with the parent case from the 7.62×39.