0NE 5.56 MM ELP MB4-BT MULTI BALL 4 BOAT TAIL CARTRIDGE. HEADSTAMP WINCHESTER 223 REM. 45g. MB4-BT (Multi-Ball 4 Boat Tail) projectile with a 4-Steel Ball core (Not Brass Balls, and not only 2. Because of specialized Product Engineering the composite projectile to separate on stiff impact compared to any other non-explosive Fragmentation projectiles in its class for controlling Ground Dwelling Critters around the ranch in this caliber along with Dirt Mound Destruction.