The .300 AAC Blackout (designated as the 300 BLK by the saam and 300 AAC Blackout by the CIP, also known as 7.62×35mm, is an intermediate cartridge developed in the United States by (AAC) for use in the M4 carbine. The cartridge yields increased performance in shorter barrels and effective subsonic performance for silencer use when compared to 5.56x45 mm The 300 AAC Blackout uses standard 5.56mm NATO magazines and components with the exception of the barrel.
The AR47 pistol is chambered in 7.62x39mm and is a well-known cartridge for having high stopping power. The AR47 has a modular design following the versatility of the AR platform, with all of the same features and functionalities as a typical AR-15 that would be chambered in 5.56x45mm. The 7.62x39mm round is known to have some serious knockdown power or kinetic energy delivery on the target, even out of a shorter barrel. The standard weight for 7.62x39mm ammunition is 122–125 grains, though 150-grain projectiles can be found as well in the market. In terms of effectiveness, it's almost on par with the cutting-edge .300 AAC Blackout cartridge. Yes, the .300 BLK was developed to function similarly to the venerable 7.62x39mm round, but in a package that could be chambered by the AR-15 with minimal modification. When firing at a target from less than 300 meters away, the 7.62x39 round is more effective since it delivers more energy to the target. Outside of that, however, the hefty round rapidly loses its force versus much lighter rounds such as 5.56x45mm NATO.