Delivering a heavy-hitting .30 caliber round on target, .300 BLK was originally designed around being a subsonic round for use in shorter barrel, suppressed rifles. Additionally, .300 BLK set out to utilize as many M4/AR15 parts and ammo components as possible. Great for home defense and suppressed use in subsonic loadings. Built on the Mk4 AR15 platform. Features EML handguard, full length M-LOK slots on both sides and the bottom of the handguard as well as M-LOK between the top picatinny rail sections; ZEROED parts including: pistol grip, drop-in trigger, 60/90 degree ambi safety, ambi mag catch, extended mag release button, muzzle brake AR15- bolt catch, polymer dust cover and ambi charging handle. Includes Magpul 30rd PMAG.