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. You have the benefit of being able to fire both super and subsonic loads of differing energy levels, suppressed and unsuppressed.The APC300 features an adjustable gas valve positioned forward of the handguard. B&T USA APC300 .300 AAC Blackout 8.7" Barrel Black 30 Round