The 300BLK cartridge has quietly made a name for itself within the professional community and its use among special operators" both military and law enforcement" has been steadily on the rise. The reasons are simple; the cartridge offers a Hollywood quiet sound signature when firing subsonic loads suppressed and with a magazine change to supersonic loads" it offers near AK47 terminal performance in real-time. Given the 300BLK's diverseness and optimization for short" sub-9-inch barrel lengths" makes it an ideal urban assault rifle cartridge. The APC300 shares all the same dialed-in ergonomics" handling and modularity features and benefits that has made the APC9 so popular but chambered in the versatile 300BLK cartridge. The benefits of being able to fire both super and subsonic loads of differing energy levels" suppressed and unsuppressed did not come without some engineering challenges along the way. The APC300 features an adjustable gas valve positioned forward of the handguard" allowing the user to select the amount of gas introduced into the system" making the platform easily tunable for ammo/suppressor combinations. Given the similarities in size" weight" and ergonomics between the APC300 and APC223/556 platforms" many customers utilize the latter as training weapons and reserve the APC300 as an operational weapon. This saves the customer a substantial amount of money given the cost of specialized 300BLK ammunition.