Features and Specifications: Caliber: 5.56 NATO Bullet Type: Full Metal Jacket (FMJ) Bullet Weight: 55 Grains Rounds: 20 Rounds per Box Muzzle Velocity: 3270 FPS Muzzle Energy: 1306 ft/lbs Bullet Diameter: .224 Bullet Ballistic Coefficient: .267 Casing: Brass Features: Proven Accuracy Positive Functioning No Barrel Leading Usage: Target, Range