Firing .223 Remington cartridges in a firearm chambered for .300 Blackout can lead to catastrophic results, including damage to the firearm and potentially serious injury to the shooter and those nearby. This is because the .300 Blackout cartridge uses a significantly larger-diameter bullet than the .223 Remington, despite both cartridges often using the same parent casing. A .223 Remington round fired in a .300 Blackout chamber will allow the smaller bullet to pass through the improperly sized bore, leading to unpredictable and dangerous pressure spikes and projectile instability.
Understanding the incompatibility of these two cartridges is crucial for firearm safety. While they may appear similar due to shared lineage, their internal dimensions and pressure characteristics differ substantially. Ignoring this critical difference can have severe consequences. The practice of developing new cartridges from existing ones is common in firearms history, often to achieve specific ballistic performance goals. However, this practice necessitates clear identification and segregation of ammunition to prevent dangerous mix-ups.
