This ammuntion is packaged and sold as cases of 250 centerfire cartridges that are all brass casings.
These 200 gr. .300 AAC Blackout subsonic cartridges feature the REX projectile made by Maker Bullets. Their attention to science and precision is unmatched and it definitely shows in the ballistics. These projectiles are top choice for subsonic hunting and defense by professionals all over. They perform best in AR platforms with barrels that are 12" or less.
Other known names for this cartridge are .300 AAC, .300 BLK, .300 Blackout, and 7.62x35mm.
If this subsonic ammunition will be discharged in a gas operated firearm it is STRONGLY recommended that such firearm incorporates the shortest length gas system possible (in most cases pistol length) or at the least an oversized gas port with an adjustable gas block installed to ensure proper functioning.